FIRST LECTURE. 



colorless globular lymphoid cell. It also occurs in the blood 

 (Fig. io, d), and is at last transformed into a disc-shaped 



Fig. 9. — Pigmented connective- 

 tissue corpuscle (stellate pigment 

 cell from the mammalial eye). 



a 



jpJm* 



a 



Fig. 10. — Disc-shaped cells 

 of human blood, a, a, a. At b, 

 half from the side ; at r, seen 

 entirely from the side ; d, lym- 

 phoid cell. 



structure {a,b, c), whose cell body contains a homogeneous red 

 substance, of an extremely complicated chemical constitution, 

 haemoglobin. Other cells subsequently become reservoirs 

 of fatty matters, often in a high degree. 



We now pass to the kernel or nucleus. Its medium 

 diameter may be assumed to be from 0.007 to 0.005 mm - It is 

 originally a vesicle (Figs. 4 and 5), that is, a structure en- 

 veloped by a delicate covering. Nucleoli occur singly, double, 

 or in greater number (Auerbach). Attention has very recently 

 been directed to a circle of small molecules deposited between 

 the nucleolus and the wall of the nucleus, and called the 

 granule-sphere. 



The nucleus may subsequently lose this vesicular character 

 and assume a different arrangement. Thus it not unfrequently 

 changes, later, into a firmer, more homogeneous structure 

 (Fig. 7), or becomes granular. Should the growing cell be- 

 come considerably lengthened, the nucleus also frequently 

 assumes a more elongated form. 



As a rule, the nucleus remains a definite, tolerably con- 

 servative constituent of the cell. Nevertheless, we meet with 

 others of the latter which have lost by age the nucleus of an 

 earlier period of life. Such non-nucleated cells form the most 



