298 SUMMARY OF CURRENT RESEARCHES RELATING TO 



are favoured by the presence of a subjacent pigmentary layer. The 

 blue of most vertebrate animals is produced by phenomena identical 

 with those manifested by disturbed media. The physical constitution 

 is the same in both cases. The pigments are bodies varying in pro- 

 perties and composition. Changes of colour are most frequently due 

 to impressions on the retina. The pigmentary granules of the chromo- 

 blasts are set in motion by the chromato-motor nerves. The chromatic 

 apparatus shows graded degrees of development in the various forms 

 showing rapid changes of colour. Among the vertebrates having this 

 apparatus in perfection (Batrachians and Reptiles), the blue colour 

 seems connected with the state of dilatation of the black chromoblasts 

 (temporary structural coloration). Bodies showing phenomena of color- 

 ation are in final analysis excretory products manifested under different 

 forms (pigment, cuticle, etc.). According to their optical properties, 

 it is determined whether it is to be the play of light (structural colour) 

 or phenomena of absorption (pigment) by which they appear. Thus 

 the aspect of coloration is the direct consequence of the state in which 

 the excretory products present themselves. 



Supra-cricoid Cartilage in Man.* — J. Citelli has found in certain 

 subjects a small cartilage above the cricoid, and between the two inter- 

 arytenoid muscles. This, he states, is not simply an anatomical varia- 

 tion, it is the homologue of the " procricoid " of Dubois, which is 

 present in Amphibians, Reptiles, Monotremes, Marsupials, all Carnivora, 

 except hyaena, some Ungulates, etc. It is rare in higher orders. 



Occipital Region of Cerebral Hemisphere in Man and Apes.f — 

 (I. E. Smith calls attention to a means not only of checking the evidence 

 of mere surface anatomy, but also of absolutely demonstrating the 

 homology of the sulcus lunatus of the human brain with the Affen- 

 spalte. This new criterion is afforded by the study of the distribution 

 of the stria Gennari in the occipital cortex. This white line is so 

 sharply defined in part of the occipital cortex in man and the apes, that 

 the stria-bearing region can be mapped out in sections of the fresh 

 brain with absolute exactness. The homology of this area can be 

 assumed in all Primates. The author further emphasises the presence 

 of a definite sulcus prrestriatus in most human brains (as well as in all 

 Prosimiae, Carnivora, Ungulata, and many other mammals) ; the absence 

 or subsidiary importance of this sulcus praestriatus (vel calcarinus pro- 

 prius) in all apes — Hapalidae, Cebidae, Cercopithecidas, and Simiidaa ; 

 the definite limbic relation of the margins of the occipital operculum 

 (overhanging the sulcus lunatus) and of the inferior occipital operculum 

 (overhanging the sulcus infrastriatus) to the lateral area striata ; the 

 presence in most human brains (and occasionally in those of the apes) 

 of superior and inferior limiting sulci of the mesial part of the area 

 striata ; and the series of intrastriate sulci, which extend along the 

 axis of the area striata both in its mesial and its lateral parts. The 

 author adopts a new nomenclature in order to emphasise the distinctive 

 relations of the various occipital sulci to the cortical area containing the 

 stria Gennari ; and to call attention to the bewildering misuse of terms 



* Anat. Anzeig., xxiv. (1903) pp. 289-96. f Tom. cit., pp. 436-51. 



