EXPLANATION OF THE PLATES. 461 



continued directly across, as the lining of the original nervous roof. The abrogation of 

 the nervous portion of that roof permitted the intrusion of the pia (or of its vessels) to 

 form the portiplexus, upon which the endyma is reflected. 



The boundaries of the porta are, then, as follows : caudal, the thalamus ; cephalic, the 

 fornix ; ventral, the continuity of the two ; dorsal, the endyma, reflected upon the porti- 

 plexus. 



EXPLANATION OF THE PLATES. 



§ 1158. The four lithographic plates of the brain illustrated the 

 senior author's paper {H) in the Proceedings of the Philosophical 

 Society of Philadelphia, by courtesy of which they are included in 

 the present work. With slight alterations, the following explana- 

 tions are the same as given in that paper, but quotation marks are 

 used only where specially needed. 



As with the other figures of the brain, all of the preparations from which the figures 

 were drawn are in the Museum of Cornell University, and are accessible for examination 

 to those who may desire to verify the figures or the descriptions. 



In most cases, each figure is based upon more than one preparation. Encephalotomists 

 need not be reminded of the diflBculty of obtaining a preparation which shows many points 

 of structure equally well. Since the present account is only general, and does not aim to 

 indicate individual peculiarities, or those of sex, breed or age, most of the figures may be 

 regarded as representing what may be called an average cat's brain. It is obvious that a 

 very large number of specimens would need to be carefully compared in order to confer 

 upon any generalization respecting sex, etc., a trustworthy character. 



" Most of the figures are twice the diameter of the preparations, and, with the excep- 

 tion of Fig. 1 and 2, it would have been better to make the enlargement four or five 

 diameters. Aside, however, from the greater expense which this would have involved, 

 such a degree of enlargement would have rendered it not only possible but necessary to 

 show certain details of structure upon which my information is, at present, imperfect. 



" All of the figures have been drawn from my own preparations by Miss G. D. Clem- 

 ents, B. S., at the time a student in the Natural History Course in Cornell University. 



" Artists and anatomists who have undertaken to represent the details of encephalic 

 structure understand the difficulties of the task, and will admit that the omissions and 

 inaccuracies to which attention is called in the descriptions are both few and unimportant 

 compared with the general thoroughness of the work. Indeed, for all the deficiencies, I 

 hold myself much more responsible than the artist, by whom some of the figures were 

 drawn at least four times, twice upon stone." 



The abbreviations are explained in §§ 1137, 1128 ; synonyms, references and brief 

 descriptions are given in the latter part of this chapter (§§ 1181-1333). 



PLATE I. 



§ 1159. Fig. I. — The dorsal aspect of the brain ; x2. 



" The general form and some of the fissures are drawn from Prep's 288 and 289, the 

 bisected brain of a white and Maltese $ ; but the fissures of the right hemisphere are 

 derived from several different preparations. 



