254 



SCIENCE. 



FURTHER NOTES ON THE BRAIN OF THE 

 SAUROPSIDA. 

 By E. C. Spitzka, M. D. 



1. A most notable feature of the cerebral hemispheres 

 of such reptiles as the Alligator, Iguana and sea-turtle is 

 the absence of a proper choroid plexus in the lateral ven- 

 tricle. This is the more remarkable as in the amphibia, 

 the cnoriod plexus is very well developed. The sea-turtle 

 has a few vascular coils protruding into the lateral ven- 

 tricle at its posterior portion ; nothing of the kind can be 

 identified in the Iguana or in birds. 



2. On removing the inner cerebral wall of an Alligator's 

 hemisphere it can be seen that the Corpus Striatum is 

 continued into the pedicle of the olfactory bulb, as a dis- 

 tinct prominence. In fact the substance of the pedicle is 

 in the main a continuation of the Corpus Striatum and of 

 the basilar part of the hemisphere, the dorso-lateral cor- 

 tex becoming attenuated to a mere film on entering that 

 structure. The lumen of the pedicle is a continuation of 

 that recess of the lateral ventricle which undermines the 

 mesal side of the root of the Corpus Striatum. 



3. The Corpus Striatum is relatively more massive in 

 the Sauropsida, than in any other animal group. It 

 reaches its maximum in birds, where also the lateral ven- 

 tricle is most reduced. It seems as if a secondary fusion 

 must occur, as explaining the apparent obliteration noted 

 in the latter group. 



4. A careful study of the structure designated as the 

 anterior commissure of the reptile's brain, has failed to 

 convince me that this structure is to be considered as the 

 homologue of the same commissure in the mammalian 

 brain. So far I am inclined to consider it as represent- 

 ing the Corpus Callosum, at least in part. Its fibres are 

 medullated. 



5. The inner face of the hemispheric wall is finely stri- 

 ated ; this is due to the fasciculation of the nerve fibres 

 lying subjacent to the ventricle ; they correspond to the 

 Corona radiata. 



6. It is not difficult to see that the greater part of the 

 cerebral surface, that is, the entire basilar and more than 

 half of its lateral aspect is the representative of what in 

 the mammalia is the least voluminous and functionally 

 the least important portion, namely of the Island of Reil 

 and the praeperforate region. In some reptiles (Chely- 

 dra, Boa) these two districts or their homologues are de- 

 marcated from each other by a shallow sulcus. The 

 area homclogous with the Island of Reil, corresponds 

 pretty accurately to the base of the Corpus Striatum ; 

 the other, represented in mammals by the Substantia 

 pcrjorata anterior is a bodily continuation of the thal- 

 amic halves, a marked constriction separates them from 

 the thalami proper, on the dorsal surface. Perhaps they 

 constitute a species of prothalamus. 



There remains then as the representative of the convo- 

 luted portion of the cerebral hemispheres of the placental 

 mammalia, merely the delicate thin walled portion of the 

 reptilian ccebrum. It is here where the pyramidal nerve 

 cells are tound in the best development. In the tenuity 

 of the subjacent nerve layer, it closely resembles the 

 hemispheric wall of the mammalian embryo. 



7. There are two varieties of cerebelh found in the 

 Sauropsida; to these might be added a third or funda- 

 mental type from which the other or divergent types may 

 be derived. 



The fundamental type is found in serpents and apodal 

 lacertians, as well as in Chelonia of a low type (Boa, 

 Bascanion, Pseudopus, Chelydra). Here the cerebellum 

 is a mere lip covering the entrance to the mesencephalic 

 ventricle, as in the Amphibia, and in embryos. 



The second type is found in the higher Chelonia (Cis- 

 tudo, Naunemys, Calemys, Thalassochelys) and the 

 Crocodilia (Alligator). Here the lip has become inflated, 

 and extends like a hollow hood directly backwards over 

 the fourth ventricle. It corresponds in its best develop- 



ment to nothing so much as to a baseball cap. This re- 

 semblance is heightened by the presence in the Alligator 

 and Thallassochelys of a distant rim. I have found, in an 

 individual of Cistudo, the Cerebellar cap dented from 

 above, and turned inside out, as it were ; the individual 

 had suffered prolonged starvation. 



The third variety is found in lacertians (Iguana) and 

 birds (Struthio, Aro, Trichoglossus, Gallus, Columba, 

 Phoenicopterus, etc). Here the cerebellar lip creeps up, 

 as it were, on the posterior declivity of the optic (and post 

 optic) lobes, firmly tied down to these by the arachnoid. 

 In birds the lip becomes reflected from the highest point, 

 and descends backwards. 



The highest form of the second variety is found in the 

 Alligator, where in the adult and in larger specimens, 

 though not in the one or two-year-olds, there are distinct 

 transverse sulci. In the sea-turtle an indication of trans- 

 verse sulci is observed in hardened specimens; they may 

 be artifacts, however. , 



8. An important feature of the reptilian brain are the 

 lateral eminences of the Oblongata, which, from their 

 connection with the eighth pair of cranial nerves, merit 

 the designation of eminentia acustica. A reliquary frag- 

 ment in the mammalia constitutes the Fasciola cinerea. 

 But the greater portion of this, in reptiles (Alligator, 

 Iguana) exceedingly complicated body seems to be a sort 

 of herald of a higher cerebellar development, and the 

 very similar lateral bodies of the human embryonic Oblon- 

 gata appear to be swallowed up in the cerebellar mass. 

 Future research must determine whether the nuclei 

 dentati are derivable from these masses or whether some 

 of the lesser cerebellar lobules monopolize them. In the 

 Alligator they closely simulate cerebellar/i?//«. and con- 

 sist of gray and white substance. It is trom them that 

 arises the eminentia transversa ventriculi quart 'i so well 

 developed in the Iguana and Alligator. In the latter the 

 acoustic convolvuli are in morphological connection with 

 the lateral kink of the cerebellum. 



9. On comparing a series of animals beginning with 

 the Amphibia, passing thence to the Sauropsida and end- 

 ing with the mammalia, we find that there is this close 

 correspondence to a series of mammalian embryonic and 

 foetal brains, that while in the lowest types the nerve 

 fibres of the spinal cord are well provided with myelin, 

 and the Oblongata presents the same maturity of struc- 

 ture, that it is only in higher types that the Cerebellum 

 and Mesencephalon show the same or an approximate 

 histological advance which involves the Thalamus and 

 Cerebrum in their entity only in the very highest types. 

 This is an important confirmation of the laws laid down 

 by Flechsig and Meyneri. 



ASTRONOMY. 

 The Morrison Observatory. 



The Morrison Observatory— the gift of Miss Morrison, 

 a former resident of Glasgow — was bu It at Glasgow, 

 Missouri, in 1875. The building is well adap'.ed to the 

 purpose it is intended to serve, and was cons ructed un- 

 der the supervision of Prof. C. W. Pritchett, who con- 

 sulted several of the leading astronomers of the countiy 

 in preparing his plans. 



The position of the observatory is, latitude, 39 16 

 16.8" north. Longitude l h 3 m 5.93 s west of Washington. 

 The latitude was obtained from observations recently 

 made with the Transit Circle, and discussed by Prof. U.S. 

 Pritchett ; the longitude from an exchange of signals 

 made with the United States Naval Observatory in 18S0, 



For instrumental equipment, the Morrison Observatory- 

 possesses one of Clark's finest 12^ equatorials. It is of 

 17 feet focal length, and has already been the means of 

 discovering a number of faint double stars. In 1877 and 

 again in 1879, a large number of observations of the 

 satellites of Mars were obtained. Mimas has been ob- 



