THE PINEAL BODY 179 



are irregular. The pineal body of Macropus is highly vascular. 

 The larger vessels follow the lines of the connective-tissue sep- 

 tum. No concretions were observed in any part of the pineal 

 body. The impression given by the arrangement and char- 

 acter of the cells in the pineal body of this species is that of a 

 glandular structure resembling in a general way this organ in 

 reptiles and birds (fig. 84). 



2. Capra hylocrius. In this animal four types of cells may be 

 distinguished, as in the kangaroo. Here, however, the large 

 elements with a deeply staining nuclei are more abdundant and 

 a smaller number of the small cells with pycnotic nuclei are 

 observed. The arrangement of the cells is typically aciniform, 

 although there are areas in which no such disposition of the 

 cells can be made out. These portions of the pineal body, 

 therefore, in which the acini do appear stand out conspicuously 

 in contrast to the areas of the tissue in which the cellular arrange- 

 ment is more diffuse. The size of the acini varies greatly from 

 about 10 micra to 60 or 70 micra in diameter. The connective 

 tissue observed in the pineal body of the ibex is prominent both 

 because of the extensive network which it forms and also on 

 account of the unusual thickness of its trabecular strands. The 

 body is highly vascular and supplied by a rich capillary network 

 (fig. 85). 



3. Camelus dromedarius. In the camel, as in Capra hylocrius, 

 four types of cells may be differentiated, namely, the large cells 

 with deeply staining nuclei, large cells with faintly staining 

 nuclei in which nucleolus and accessory nucleoli are distin- 

 guishable, small cells with deeply staining, and small cells of 

 faintly staining nuclei. The cellular arrangement has the same 

 general appearance as in the ibex, although the tendency toward 

 the formation of acini is not as pronounced. In the main, the 

 arrangment is that of wide strands of cells bounded by irregu- 

 larly disposed trabeculae of connective tissue. The connective 

 tissue forms a prominent element in the pineal body of the camel 

 and in general resembles the connective tissue of the Persian 

 ibex. The pineal body in the camel is highly vascular. There 

 were no concretions observed in it (fig. 86). 



