38 Th. Lewis, 



and horse, occasional cells containing erythrocytes occur, and also 

 scattered masses of pigment. In the haemal lymphatic glands of the 

 dog, cat, ferret, stoat and weasel, phagocytes crammed with red blood 

 cells are frequent. In the rabbit and rat, the process is so active 

 that the sinuses are usually literally packed with phagocytes. In the 

 pig and guinea pig though I cannot be certain of having seen these 

 giant cells, yet small masses of pigment are occasionally scattered 

 over the sections. 



In birds the only glands examined have been those of the fowl, 

 and in these abundant signs of phagocytosis have been observed. 



The process however is not confined to these glands; it is occa- 

 sionally found in ordinary lymphatic glands, especially in those of the 

 rat and rabbit, less frequently in those of the sheep. It is difficult 

 to understand how the blood reaches the lymph sinuses in ordinary 

 lymphatic glands, unless indeed some communication exists between 

 these spaces and the blood capillaries. In the case of certain glands 

 in which the blood vessels have been injected, the gelatin mass has 

 occasionally been noticed in the sinuses; whether this is due to such 

 a communication, or to breaking down of the delicate capillary walls, 

 I am not prepared to say,^) 



3. Origin of Phagocytes. 



Three views have been held as to the origin of phagocytes found 

 in haemolymphatic structures. Of these the first advanced was that 

 of Schumacher, which supposed the phagocyte to be developed from 

 a reticulum cell. This view, which has lately been supported by 

 Weidenreicli, breaks down if the idea that the reticulum is composed 

 of fibrous tissue and not branched cells, is accepted. Schumacher 

 considered that the reticulum is composed of branched cells, and ad- 

 vanced the following evidence in support of the theory that they give 

 origin to phagocytes. 



He stated that different phases occur in the glands of monkeys: 

 that in one gland, great abundance of reticulum and few phagocytes 



^) Another explanation, namely that such glands are low types of haemal 

 lymphatic glands, might be offered. 



