Table 1.

Numbers and densities of total, neuronal, and microglial cells^a

Species name	Structure	Structure mass (g)	C	N	I	N/mg	I/mg	I/N	No. of samples
Dendrohyrax dorsalis	Cx	7.556	282 500 000	98 960 000	13 842 895	13 098	1832	0.140	3
Dendrohyrax dorsalis	Cb	1.918	438 500 000	360 929 350	2367 900	188 180	1235	0.007	1
Dendrohyrax dorsalis	RoB	3.328	197 138 000	44 671 471	10 982 209	13 423	3299	0.246	3
Dendrohyrax dorsalis	Ctx	6.830	257 310 000	90 644 478	12 325 149	13 272	1805	0.136	2
Dendrohyrax dorsalis	Hp	0.726	25 190 000	8312 700	1516 438	11 450	2089	0.182	1
Dendrohyrax dorsalis	Br	12.802	918 138 000	504 551 401	27 176 885	39 412	10 129	0.052	7
Elephantulus myurus	Cx*	0.450	46 970 000	21 847 255	1052 128	48 549	2338	0.048	3
Elephantulus myurus	Cb	0.168	112 681 000	89 312 372	822 571	531 494	4896	0.009	2
Elephantulus myurus	RoB	0.401	43 010 000	14 012 533	1324 708	34 520	3295	0.095	2
Elephantulus myurus	Ctx	0.356	34 554 000	16 422 814	580 507	46 132	1631	0.035	2
Elephantulus myurus	Hp*	0.086	12 080 000	5159 368	353 944	59 993	4116	0.069	1
Elephantulus myurus	Br*	0.958	195 628 000	124 766 317	2699 666	130 236	2818	0.022	7
Loxodonta africana	Cx	2847.954	160 509 115 478	5593 241 033	11 667 281 742	1964	4192	2.086	264
Loxodonta africana	Cb	1171.63	287 226 757 500	250 708 527 536	7025 615 044	213 983	5982	0.028	80
Loxodonta africana	RoB	564.674	28 148 254 366	741 704 844	1947 975 176	1314	3450	2.626	44
Loxodonta africana	Ctx	2823.530	157 990 215 478	5556 610 521	11 462 555 196	1968	4149	2.063	263
Loxodonta africana	Hp	24.426	1763 900 000	36 630 512	199 354 517	1500	8175	5.442	1
Loxodonta africana	Br	4168.620	477 844 127 344	257 043 473 412	20 919 937 679	56 071	4562	0.081	388
Petrodromus tetradactylus	Cx	1.239	74 433 000	33 947 000	3908 787	27 236	3019	0.115	4
Petrodromus tetradactylus	Cb	0.304	145 311 000	110 653 150	1278 737	362 537	4206	0.012	2
Petrodromus tetradactylus	RoB	0.894	40 436 000	12 231 811	1217 665	13 696	1845	0.100	2
Petrodromus tetradactylus	Ctx	0.968	60 480 000	27 651 699	2921 184	28 566	3018	0.106	2
Petrodromus tetradactylus	Hp	0.272	13 953 000	6294 000	1067 062	23 164	3032	0.170	2
Petrodromus tetradactylus	Br	2.440	260 180 000	156 830 795	6564 788	64 104	2743	0.042	8
Procavia capensis	Cx	10.478	564 554 000	197 933 000	38 108 306	19 134	3637	0.193	6
Procavia capensis	Cb	2.058	579 378 000	488 3703 000	7806 491	242 415	3801	0.016	2
Procavia capensis	RoB	4.317	232 343 000	69 358 240	11 199 666	16 436	2594	0.161	4
Procavia capensis	Ctx	9.184	488 188 000	171 217 186	33 099 146	18 643	3604	0.193	4
Procavia capensis	Hp	1.294	76 311 438	26 712 953	4994 695	21 712	3860	0.187	2
Procavia capensis	Br	16.853	1376 275 000	755 653 256	57 043 095	45 576	3389	0.075	12
Antidorcas marsupialis	Cx	68.806	4443 685 152	396 896 159	268 018 858	5768	3791	0.675	29
Antidorcas marsupialis	Cb	11.458	2724 458 750	2257 214 074	58 539 299	196 999	5147	0.026	2
Antidorcas marsupialis	RoB	25.810	1389 765 624	70 485 000	84 309 976	2731	3267	1.196	3
Antidorcas marsupialis	Ctx	65.372	4216 083 590	376 412 018	254 974 497	5758	3790	0.677	28
Antidorcas marsupialis	Hp	3.434	227 601 562	20 484 141	12 973 289	5965	3778	0.633	1
Antidorcas marsupialis	Br	106.074	8557 909 526	2724 595 233	402 984 165	25 686	3810	0.148	34
Giraffa camelopardalis	Cx	398.808	29 244 220 002	1730 513 460	2430 910 509	4339	6330	1.405	45
Giraffa camelopardalis	Cb	67.730	14 398 437 500	8878 076 563	298 047 656	131 080	4401	0.034	1
Giraffa camelopardalis	RoB	70.680	5021 562 500	142 697 625	495 014 837	2019	7005	3.469	5
Giraffa camelopardalis	Ctx	391.322	28 341 393 752	1671 925 960	2365 907 262	4272	6278	1.415	44
Giraffa camelopardalis	Hp	7.486	681 250 000	58 587 500	64 786 875	8435	9327	1.106	1
Giraffa camelopardalis	Br	537.218	48 442 643 752	10 751 287 650	3335 932 264	19 678	6278	0.310	51
Sus scrofa domesticus	Cx	42.202	3476 643 442	307 082 404	388 217 638	7276	9048	1.264	24
Sus scrofa domesticus	Cb	8.128	2207 031 250	1858 320 313	85 632 813	228 632	10 536	0.046	1
Sus scrofa domesticus	RoB	13.850	1155 531 250	58 709 836	129 924 626	4238	9386	2.213	3
Sus scrofa domesticus	Ctx	40.274	3300 354 380	289 142 456	359 715 940	7179	8932	1.244	23
Sus scrofa domesticus	Hp	1.928	146 289 062	12 907 084	22 141 064	6692	11 480	1.715	1
Sus scrofa domesticus	Br	64.180	6839 205 942	2224 112 553	598 831 830	34 654	9310	0.269	28
Tragelaphus strepsiceros	Cx	213.370	13 064 871 626	762 567 178	837 474 821	3574	3718	1.098	37
Tragelaphus strepsiceros	Cb	31.776	5308 593 750	4042 494 141	96 616 406	127 218	3041	0.024	1
Tragelaphus strepsiceros	RoB	61.716	3515 369 752	106 590 230	284 487 989	1727	4485	2.669	5
Tragelaphus strepsiceros	Ctx	202.434	12 392 809 376	726 411 196	799 590 074	3588	3772	1.101	36
Tragelaphus strepsiceros	Hp	10.936	535 156 250	28 363 281	29 326 563	2594	4710	3.946	1
Tragelaphus strepsiceros	Br	306.860	21 751 929	4911 651 549	1204 929 478	16 006	3800	0.245	43
Canis familiaris	Cx	65.491	3944 367 750	527 911 882	313 577 236	8061	4788	0.594	86
Canis familiaris	Cb	7.512	2525 312 500	1676 633 212	48 233 469	223 194	6421	0.029	2
Canis familiaris	RoB	13.459	976 243 750	48 149 310	103 384 213	3577	7681	2.147	6
Canis familiaris	Ctx	63.481	3801 711 500	519 305 298	302 616 235	8180	4767	0.583	84
Canis familiaris	Hp	2.010	142 656 250	8606 584	11 141 453	4282	5543	1.295	2
Canis familiaris	Br	86.462	7445 924 000	2252 694 404	465 370 250	26 054	5382	0.207	94
Felis catus	Cx	24.176	1346 938 750	249 834 196	73 677 550	10 334	3048	0.295	44
Felis catus	Cb	5.110	1269 000 000	942 902 390	21 826 800	184 521	4271	0.023	1
Felis catus	RoB	5.572	328 062 500	22 472 558	10 202 744	4033	1831	0.454	3
Felis catus	Ctx	23.300	1282 938 750	241 786 292	71 716 276	10 377	3078	0.297	43
Felis catus	Hp	0.876	64 000 000	8047 904	1952 000	9187	2228	0.243	1
Felis catus	Br	34.858	2944 001 250	1215 209 144	105 689 645	34 862	3032	0.087	48
Mungos mungo	Cx**	NA	NA	NA	NA	NA	NA	NA	20
Mungos mungo	Cb	1.548	470 000 000	315 738 964	8695 000	203 966	5617	0.028	1
Mungos mungo	RoB	3.454	174 060 000	22 514 320	6614 280	6518	1.915	0.294	3
Mungos mungo	Ctx**	NA	NA	NA	NA	NA	NA	NA	19
Mungos mungo	Hp	0.428	25 625 000	2664 224	863 563	6225	2018	0.324	1
Mungos mungo	Br	NA	NA	NA	NA	NA	NA	NA	24
Mustela putorius furo	Cx	3.123	303 008 200	38 952 070	20 392 452	12 473	6530	0.524	24
Mustela putorius furo	Cb	0.920	430 860 000	351 264 942	8832 630	381 810	9601	0.025	2
Mustela putorius furo	RoB	1.386	143 542 500	14 210 998	12 847 054	10 253	9269	0.904	4
Mustela putorius furo	Ctx	2.794	270 508 200	35 760 238	17 528 931	12 799	6274	0.490	22
Mustela putorius furo	Hp	0.329	32 500 000	3191 834	2856 750	9702	8683	0.895	2
Mustela putorius furo	Br	5.429	877 410 700	404 428 012	42 115 714	74 494	7758	0.104	30
Panthera leo	Cx	139.902	7806 210 250	545 238 686	795 452 825	3897	5686	1.459	107
Panthera leo	Cb	24.882	7093 750 000	4049 750 938	124 140 625	162 758	4989	0.031	1
Panthera leo	RoB	34.162	2165 910 000	72 045 082	210 743 043	2109	6169	2.925	2
Panthera leo	Ctx	136.254	7615 560 250	531 700 630	784 402 706	3902	5757	1.475	106
Panthera leo	Hp	3.648	190 650 000	13 538 056	10 886 115	3711	2984	0.804	1
Panthera leo	Br	198.946	17 065 870 250	4667 034 704	1129 760 611	23 459	5679	0.242	110
Ursus arctos	Cx	222.000	10 404 967 500	250 969 270	843 842 866	1130	3801	3.362	116
Ursus arctos	Cb	45.106	11 550 000 000	9253 250 478	188 265 000	205 145	4174	0.020	1
Ursus arctos	RoB	47.898	2743 825 000	81 384 332	98 777 700	1699	2062	1.214	4
Ursus arctos	Ctx	217.870	10 147 192 500	242 359 888	835 113 943	1112	3833	3.446	115
Ursus arctos	Hp	4.130	257 775 000	8609 382	8815 905	2085	2135	1.024	1
Ursus arctos	Br	315.004	24 698 792 500	9585 604 080	1131 204 697	30 430	3591	0.118	121
Dendrolagus goodfellowi	Cx	19.570	1532 188 750	273 434 984	80 439 909	13 972	4110	0.294	46
Dendrolagus goodfellowi	Cb	4.236	1545 500 000	1237 018 200	10 200 300	292 025	2408	0.008	1
Dendrolagus goodfellowi	RoB	7.742	518 100 000	37 858 500	29 687 130	4890	3835	0.784	2
Dendrolagus goodfellowi	Ctx	18.820	1431 388 750	255 280 904	74 289 076	13 965	4064	0.291	45
Dendrolagus goodfellowi	Hp	1.290	100 800 000	18 154 080	6189 120	14 073	4798	0.341	1
Dendrolagus goodfellowi	Br	31.548	3595 788 750	1548 311 684	120 458 923	49 078	3818	0.078	49
Didelphis aurita	Cx	2.136	163 477 500	42 499 454	11 581 340	19 897	5511	0.273	31
Didelphis aurita	Cb	0.778	375 031 250	334 265 353	5362 947	429 647	6893	0.016	1
Didelphis aurita	RoB	1.378	108 137 500	15 732 651	8326 588	11 417	6043	0.529	3
Didelphis aurita	Ctx	1.750	133 775 000	35 269 454	9740 554	20 154	5679	0.276	30
Didelphis aurita	Hp	0.386	30 000 000	7230 000	1848 000	18 731	4788	0.256	1
Didelphis aurita	Br	4.292	643 138 750	392 497 458	25 297 939	91 449	5961	0.064	35
Macropus fuliginosus	Cx	40.194	2740 637 500	370 171 727	161 697 613	9210	4023	0.437	54
Macropus fuliginosus	Cb	7.358	2721 875 000	1989 962 813	22 863 750	270 449	3107	0.011	1
Macropus fuliginosus	RoB	15.172	1245 625 000	97 741 950	80 965 625	6442	5337	0.828	2
Macropus fuliginosus	Ctx	37.256	2513 387 500	325 403 477	145 776 475	8734	3913	0.448	53
Macropus fuliginosus	Hp	2.938	227 250 000	44 768 250	15 975 675	15 238	5438	0.357	1
Macropus fuliginosus	Br	62.724	6708 137 500	2457 876 490	265 642 245	39 186	4235	0.108	57
Macropus parma	Cx	9.914	869 532 500	135 625 473	48 259 054	13 680	4868	0.356	35
Macropus parma	Cb	1.690	721 687 500	558 080 944	5268 319	330 225	3117	0.009	1
Macropus parma	RoB	4.110	352 250 000	17 420 050	20 254 375	4238	4928	1.163	2
Macropus parma	Ctx	8.676	750 782 500	127 146 723	40 467 177	14 655	4664	0.318	34
Macropus parma	Hp	1.238	118 750 000	8478 750	7801 875	6849	6302	0.920	1
Macropus parma	Br	15.714	1943 470 000	711 126 467	73 851 860	45 254	4700	0.104	38
Macropus rufogriseus	Cx	16.102	1423 953 750	256 784 370	98 537 600	15 947	6120	0.384	41
Macropus rufogriseus	Cb	3.572	1479 625 000	1022 568 838	13 612 550	286 273	3811	0.013	1
Macropus rufogriseus	RoB	7.320	571 812 500	42 476 569	36 538 819	5803	4992	0.860	2
Macropus rufogriseus	Ctx	14.306	1259 953 750	246 009 570	84 038 915	17 196	5874	0.342	40
Macropus rufogriseus	Hp	1.796	164 000 000	10 774 069	14 514 000	5999	8081	1.347	1
Macropus rufogriseus	Br	26.994	3475 391 250	1321 829 777	148 746 746	48 968	5510	0.113	44
Macropus rufus	Cb	4.786	1976 624 000	1532 871 912	31 230 659	320 282	6525	0.020	1
Macropus rufus	P + M	2.886	227 500 000	19 337 500	17 881 500	6700	6196	0.925	1
Marmosops incanus	Cx	0.408	57 975 000	20 413 493	2811 788	50 033	6892	0.138	2
Marmosops incanus	Cb	0.158	106 500 000	82 399 050	788 100	521 513	4988	0.010	1
Marmosops incanus	RoB	0.344	35 825 000	9238 790	2332 208	26 857	6780	0.252	3
Marmosops incanus	Ctx	0.348	51 700 000	17 831 330	2553 980	51 239	7339	0.143	1
Marmosops incanus	Hp	0.060	6275 000	2582 163	258 530	43 036	4309	0.100	1
Marmosops incanus	Br	0.910	200 300 000	112 051 333	5928 880	123 133	6515	0.053	6
Metachirus nudicaudatus	Cx	0.992	84 775 000	20 191 038	2653 458	20 354	2675	0.131	2
Metachirus nudicaudatus	Cb	0.342	166 312 500	134 131 031	1729 650	392 196	5057	0.013	1
Metachirus nudicaudatus	RoB	0.674	66 256 250	11 272 337	3670 596	16 725	5446	0.326	3
Metachirus nudicaudatus	Ctx	0.848	72 625 000	15 999 288	2222 325	18 867	2621	0.139	1
Metachirus nudicaudatus	Hp	0.144	12 150 000	4191 750	428 895	29 109	2978	0.102	1
Metachirus nudicaudatus	Br	2.008	317 343 750	166 594 406	8060 531	82 467	4014	0.049	6
Sarcophilus harrisii	Cx	5.228	437 941 000	71 655 547	9547 114	13 706	1826	0.133	26
Sarcophilus harrisii	Cb	1.434	735 437 500	601 073 069	7722 094	419 158	5385	0.013	1
Sarcophilus harrisii	RoB	3.140	276 752 500	20 966 121	5590 401	6677	1780	0.267	3
Sarcophilus harrisii	Ctx	4.594	367 941 000	59 013 547	7248 438	12 846	1578	0.123	25
Sarcophilus harrisii	Hp	0.634	70 000 000	12 642 000	2275 000	19 940	3588	0.180	1
Sarcophilus harrisii	Br	9.802	1450 131 000	693 694 737	22 912 070	70 771	2337	0.033	30
Wallabia bicolor	Cx	15.182	1239 254 750	208 113 314	95 174 765	13 708	6269	0.457	45
Wallabia bicolor	Cb	4.420	1528 750 000	1195 941 125	26 141 625	270 575	5914	0.022	1
Wallabia bicolor	RoB	10.410	687 750 000	31 865 550	54 676 125	3061	5252	1.716	2
Wallabia bicolor	Ctx	13.616	1115 954 750	195 142 154	88 272 021	14 332	6483	0.452	44
Wallabia bicolor	Hp	1.566	123 300 000	12 971 160	6892 470	8283	4401	0.531	1
Wallabia bicolor	Br	30.012	3455 754 750	1435 919 989	175 897 917	47 845	5861	0.122	48
Aotus trivirgatus	Cx	9.124	1303 931 000	451 671 982	23 875 354	49 504	2635	0.053	43
Cebus apella	Cx	53.784	3035 947 220	970 159 664	106 083 459	18 038	1991	0.109	78
Homo sapiens sapiens	Cx	696.708	58 983 401 216	9547 198 728	1634 984 719	13 703	2403	0.171	290
Homo sapiens sapiens	Ctx	693.422	58 732 501 216	9513 780 748	1612 228 351	13 720	2381	0.169	271
Homo sapiens sapiens	Hp	3.286	250 900 000	33 417 980	10 136 360	10 170	3085	0.303	19
Macaca fascicularis	Cx	40.000	4755 230 252	1404 683 000	192 394 153	35 117	4727	0.137	79
Macaca nemestrina	Cx	76.964	7787 044 390	2194 785 386	277 022 786	28 517	3668	0.126	106
Otolemur garnettii	Cx	4.876	494 053 510	196 070 964	39 378 618	40 211	8294	0.201	23
Papio anubis cynocephalus	Cx	94.744	4934 116 014	1144 837 998	257 818 766	12 083	2773	0.225	102
Saguinus midas	Cx	5.030	603 175 002	220 924 134	16 398 445	43 921	3041	0.074	28

^aCx includes gray matter, white matter, and hippocampus; RoB includes pons, medulla oblongata, mesencephalon, diencephalon, and striatum; P + M, Pons and medulla oblongata; Ctx includes gray and white matter, excluding hippocampus; Hp, hippocampus; Br, whole brain (corresponding to the joint value of the respective Cx, Cb, and RoB); C, total number of cells in the structure; N, total number of neurons in the structure; M, total number of microglia in the structure; N/mg, number of neuronal cells per milligram of structure; I/mg, number of microglia per milligram of structure; I/N, microglia/neuron ratio. Structure mass, C, N, and N/mg list the values published previously for each species and for each structure in its entirety (Ribeiro et al., 2013; Herculano-Houzel et al., 2014; Kazu et al., 2014; Neves et al., 2014; Gabi et al., 2016; Dos Santos et al., 2017; Jardim-Messeder et al., 2017). I/mg and I/N list the values measured from the samples available for each species and structure (for some structures, some samples were no longer available for the present analysis). Absolute numbers of microglial cells (I) are estimated by applying the product of the I/N ratios measured in this study by the previously published number of neurons N in each structure and species (I/N × N). All values refer to the two hemispheres together, calculated as 2× the values obtained for one hemisphere, as in the original reports.

*Data available for only one specimen of the species.

**Samples were only available for some cortical sites, so total values were not calculated (NA). In both, however, microglial densities and ratios between numbers of neurons and microglial cells from the samples available are included in analyses across sites of the Cx. For M. rufus, only two structures were available: Cb and Pons and Medulla (P + M).