PRIMORDIAL CRANIUM OF THE CAT 285 



cance of the ala temporalis and to the formation of the hypo- 

 physeal skeleton forms the main part of the study of orbito- 

 temporal region. Concerning the origin and early history of 

 the ethmoidal skeleton of mammals comparatively little is 

 known, whereas, on the contrary, a great literatm-e exists on 

 the development of the nasal conchae, floor of the nose and 

 nasal sinuses. Cat material was found favorable for the inves- 

 tigation of many early processes of ethmoidal development, and 

 to a discussion of these, practically the whole of the section on 

 the ethmoidal region has been devoted. 



MATERIAL AND METHODS 



The present study starts with a cat embryo of 23.1 mm., 

 series no. 466 of the Harvard Embryological Collection. From 

 this, a model of the chondrocranium was reconstructed by stu- 

 dents of the Harvard Medical School under the direction of the 

 author while a teaching fellow in histology in that institution.^ 

 The model, enlarged thu'ty-three times, includes, in addition 

 to the chondrocranium, the ossifications, main bloodvessels and 

 nerves. It is an example of care and industry and as such has 

 been on the one hand invaluable as material for study and on 

 the other a reminder of the enthusiasm and earnest effort of those 

 students, then in their first year of medical study, Messrs. G. 

 D. Cutler, I. Gerber and R. D. Leonard, who responded to the 

 suggestion to undertake the labors of cranial reconstruction. 



Through the kindness of the late Professor Minot and Professor 

 F. T. Lewis, the model, together with the following series of cat 

 embryos from the collection at the Harvard Medical School, 

 was placed at my disposal in St. Louis. 



1 The model was reconstructed in 1907. The present investigation was un- 

 dertaken in St. Louis several years later but on account of interruptions its 

 progress was delayed. I take this opportunity to acknowledge the many cour- 

 tesies of Prof. J. S. Kingsley and the staff of the Marine Biological Laboratory 

 at South Harpswell, Maine, where during the summer of 1915 it was my privilege 

 to work. 



