Jan, 23, 1879] 



NATURE 



2/7 



He made drawings of the hemisphere of each species ; 

 compared, first, line for hne the hemispheres of different 

 individuals of the same species, and then took as charac- ^ 

 teristic of that species every sulcus that was constantly 

 present in all the individual hemispheres. | 



The different species in a genus and the different 

 genera in the order were compared in the same way, so 

 that by elimination he at last obtained a schematic 

 drawing of the sulci constant throughout the order. In 

 his drawings he represents those sulci peculiar to the 

 individual, species, (Sec, by variously dotted lines, those 

 running through the whole order by thick black lines. | 



Since the most constant or chief sulci are the first to \ 

 appear in the course of development, he giv^es drawings ; 

 of foetal brains of the sheep, cow, and pig. With regard : 

 to these foetal brains, it is highly important to note that 

 in no instance were transitory or temporary sulcus 

 markings met with ; Meckel himself admits that he did 

 not find these temporary sulci in brains of other animals, ; 

 though he described them in the human foetus. Dr. 1 

 Krueg regards them as entirely artificial. The following, ! 

 then, are the chief fissures or sulci {Haiiptfurcheti) constant 

 throughout the Ungulata, and of these the first six are the 

 most important in relation to those of the Camivora : — j 



1. Fissura sylvii, ant., post., processus acuminis. 



2. ,, spleniahs. j 



3. ,, supra-sylvia, ant., post., supr. I 



4. „ coronalis. ■ 



5. ,,■ praesylvia. ' 



6. ,, laterahs. 



7. ,, diagonalis. ; 



8. „ postica. i 



9. ,, genualis. I 

 10. ,, rostralis. 



h. ,, hippocampi. ■ 



rii. „ rhinalis. 1 



C.ca. Corpus callosum. 



The earliest foetus he possesses shows two fissures, 

 namely, F. sylvii and F. splenialis. The sylvian 

 fissure develops radially, just as Ecker has shown in ^ 

 the human foetus, and since in the latter, the parieto- ■ 

 occipital fissure appears almost contemporaneously with 

 the sylvian fissure, he considers the Fissura splenialis of : 

 Ungulates to be the homologue of the human parieto- ! 

 occipital. This view derives some strength from the fact | 

 that as development proceeds, the anterior extremity of ' 

 the Fissura splenialis turns upwards and gains the median \ 

 border. Moreover, here it is opposite to the processus 

 acuminis Sylvii, which is homologous with the posterior 

 or horizontal ramus of the human Sylvian fissure. 



Tie positions of the fissures are shown in the accom- 

 panying diagrams. As regards the foetal forms it is note- 

 worthy that in the Suillidae, from its earliest appearance 

 the posterior process of the F. supra-Sylvia is directed 

 downwards as well as backwards ; this we shall find is a 

 family characteristic of importance. 



Before enumerating the slighter distinctive characters 

 of the famihes, or comparing the Ungulata with the 

 Carnivora, it will be well to mention the results which are 

 of more general importance. Dr. Krueg believes that he 

 has established the followirg propositions : — 



1. That the forerunners or the adult fissures are never 

 transitory radial markings, but aUays present (though 

 incompletely) the adult fonn. 



2. That the two important fissures (F. hippocampi and 

 F. rhinalis) common ^to all mammals, are the first to 

 appear, and that next those characteristic of the Ungulata ' 

 commence. j 



It is remarkable that the fissures peculiar to the indi- 

 vidual, may appear contemporaneously with, or even 

 precede, the last few of the chief fissures. This fact of itself 

 would cast some doubt on the morphological value of 

 tliese later chief fissures, and comparison with the Catni- 

 voraalso diminishes their importance as diagnostic marks. 



3. On no occasion was a fissure once formed ever 

 broken up by a bridging convolution. The reverse of 

 this may and often does occur, viz., that two originally 

 distinct fissures may, by extension of their neighbouring 

 extremities, so mingle as to form one large fissure. From 

 this fact he concludes that when in adult brains we meet 

 with a well-known fissure bridged over, originally this 

 fissure was developed as two distinct ones. This would 

 certainly explain the remarkable cases lately published by 



Fig. I. — Median surface of typxal hemisphere. 



Henschel, in which the fissure of Rolando was bridged 

 over, and such a state of things would be due to atavism. 



4. The influence of the size of the animal on the shape 

 of the hemisphere and its details is ver>' important, and 

 may be regarded as threefold. 



(rt) The number of accessory fissures increases with the 

 size of the brain and the size of the animal. 



{U) The shape of the hemisphere differs. Thus, in the 

 larger animals it is broader, and more rounded, whereas, 

 in the smaller animals it is distinctly narrower, and tapers 

 more to a point anteriorly. 



{c) In the smaller animals it is noticed at once that 

 fissures (such as the splenialis), which in the schematic 

 brain are situated on the median surface, in these smaller 

 individuals, often appear on the upper. Such a condition 

 may be supposed to result from a rotation of the upper or 

 median border around the Island of Reil as a centre. 

 This rotation Dr. Krueg has named " supination," and 

 that in the opposite direction and occurring in the larger 

 animals "pronation.' The posterior extremity of the 

 F. coronalis almost always presents a "horn" (Biigel) 

 directed inwards. This branch becomes of importance, 

 as it often joins the F. splenialis, and offers a homology 

 with the fissura cruciata of the Camivora. 



The following are the main family characteristics : — 



TragulidcB. — Supination marked. F. coronalis com- 

 municates with the processus anterior supra-Sylvii. The 

 Tragulidas (Hke the antelopes) present strong elephantine 

 characters as regards their fissures. 



Fig. 2. Fig 3. 



Fig. 2. — Lateral outer surfaceoftypical' hemisphere. Fig. 3. — Upper surface 

 of typical hemisphere. 



Elephants. — F. coronalis communicates with the pro- 

 cessus anterior supra-Sylvii, and also either with the F. 

 splenialis or ends just behind it. 



The Giraffes present no generic characters. 



CavicornidcE. — In the majority the F. coronalis does 

 not communicate with the F. supra sylvii, the exception 

 being Bos iaums. The processus acuminis Sylvii is broken 



