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The Mammalian Cerebral Cortex, tvith Special Reference to its 

 Comparative Histology. 1. Order Insectivora. — Preliminary 

 Communication. 



By George A. Watson, M.B., CM. Edin. 

 (From the Pathological Laboratory of the London County Asylums, Claybury.) 



(Communicated by Dr. F. W. Mott, F.E.S. Eeceived July 28,— Read 

 December 14, 1905.) 



The results and conclusions brought forward in this paper form a portion of 

 the outcome of an extensive investigation dealing with the cortex cerebri in 

 various orders of mammals. The work has special reference to the neopallium 

 only, and has for its prime purpose an endeavour to shed some further light 

 upon the functional significance of the cerebral cortical lamination. 



Animals Examined and Methods of Study. 



The brains of the animals belonging to this order examined are : — 



1. The Mole (Talpa Earopea). 2. The Shrew (Sorex vidgaris). 3. The 

 Hedgehog (Erinaceus Europcus). 



The cerebral cortex has been examined by means of complete series of 

 sections cut in almost every possible direction and stained by one or other 

 modification of the Nissl method. 



As part of the method of study throughout the entire investigation, the 

 natural habits of the animals examined, and their educability, as far as facts 

 relating to the latter are available, have been considered when attempting to 

 correlate structure and function. 



Macroscopic Appearances and Microscopic Furrows. 



All are almost smooth highly macrosmatic brains. That of the Hedgehog 

 is one of the simplest mammalian brains. It presents in addition to the 

 rhinal fissure a short presylvian furrow ; the latter is not found macros- 

 copically in the Mole and Shrew, but is seen on microscopic examination of 

 sections. By this method also, in the Mole only, two shallow more or less 

 longitudinal curved furrows can be traced on the dorso-lateral aspect of the 

 hemisphere, which appear to represent foreshadowings of the corono-lateral 

 and supra-sylvian sulci. 



Signs of gi^eater differentiation of the neopallium of the Mole, as compared 

 with the Hedgehog especially, are further exhibited on microscopic exami- 

 nation of the structure of the cortex. The optic nerves in the Mole and 



