VII. VITAMIN A OKFICIEXCY IN ANIMALS 



121 



ill the clcticii'iicy is not a cause of ])resMii-e upon spinal nerxcs at toiamens 

 of exit, as is the case in dojiis.-"' -^ The histoiofiic features of the heiniatioiis 

 of brain and cerehclhini studied in the rat' are 1h( se attending ineclianical 



Fl<;. 32. Vitamin A (Icficicncy in the chick. Ilcinialions iVoni I he olfactofv lolx's 

 via iiraclmoidul villi into a confiucns sinuum (undcscrihed) formed by the confluence 

 of the saggital sinuses and veins from the oi'l)its and surfaces of the cerebral hem- 

 ispheres. 



tardation of endochondral bone formation occurs promptly in these avian species 

 willi the result that there is comjjression of the spinal cord and l)rain. Herniations 

 into arachnoidal villi of ducks and chicks are jjioininent features of the disi)roi)or- 

 tionate growth of the central nervous system and the skull. Mxcessive vitamin A 

 results in the same type of acceleration of endochondral bone growth as described 

 for mammalian sj)ecies. 



