178 FREDERICK TILNEY AND LUTHER F. WARREN 



the protoplasm. In the new-born, lobation of the gland is much 

 more easily discerned than in the later periods of life. 



The histology of the pineal body of the following mammals 

 has not heretofore been given, and as it seems to furnish some 

 details in the finer structure of the organ, the authors have 

 considered it advantageous to include these original observations 

 in this work. All of the material was obtained from the study 

 collections of the Department of Anatomy, Columbia University. 

 It includes specimens of Marcopits grayi, Camelus dromedarius, 

 <'<i />/<! hylocrius, Zalophus calif or nianus, Lepus cuniculus, and 

 Simia satyrus. In addition to these species, the later stages of 

 development in the human fetus and in Felis domestica were 

 studied. The staining methods used were the Van Giesen, 

 haematoxylin-eosin, and Weigert's iron haematoxylin. On ac- 

 count of the limited amount of tissue it was impossible to do 

 any silver impregnation so that no evidence was obtained con- 

 cerning the nature of the nerve fibers in the pineal body. 



1. Macropus grayi. In this species the cellular constituents 

 of the pineal body present the most striking features of any 

 of the mammals studied. Four types of cells are noted: 



First. Large cells with extensive cytoplasm and a large vesicu- 

 lar nucleus. The nuclei of these cells stain very deeply. 



Second. Cells of a similar size with vesicular nuclei which 

 stain feebly. 



Third. Smaller cells with a large nucleus and a very small 

 amount of cytoplasm. The nuclei are intensely basophilic. 



Fourth. Small cells with feebly staining nuclei showing many 

 granules. 



The cells of these four varieties arrange themselves in a more 

 or less distinctive manner. The large epithelial elements of 

 both types nre disposed in such a way as to form well-defined 

 acini. Interspersed between these acinous groups are more or 

 less irregularly convoluted chains or cords of cells made up of 

 both varieties of the large type. The smaller cellular elements 

 are scattered among the cords and acini in an irregular manner. 

 Trabeculae of connective tissue serve to give the impression of 

 lobiilntioii to the structure, although thcs- lines of separation 



