The Structure and Functions of the haemolymph Glands and Spleen. 29 



metliod of tracing' blood vessels seems one wliicli is scarcely likely to 

 give satisfactory results. At any rate I am unable to comfirm the 

 account given by Drummond of the vascular supply. The difficulty, 

 of being unable to identify the glands after injection, is easily re- 

 medied by noting the position of the glands before commencing the 

 operation. 



The arteries and veins have been separately injected in the rat 

 directly after death with a warm carmine gelatine mass. The animals 

 were placed on one side until the injection hardened, when the glands 

 were excised and embedded in paraffin. Serial sections of a thickness 

 of from 10 — 20 .« were then cut. 



I find that one or more arteries enter the hilum of a gland; 

 these spring in the case of the splenic group from the splenic artery, 

 and in the case of the renal group from the renal arteries (pi. I. 

 fig. 7). On reaching the capsule they break up into several branches, 

 of which one or more opens directly into the sinus. The wall of 

 such an artery is continuous with the capsule of the gland. Other 

 arteries proceed across the sinus, being conducted in the gland of a 

 rat, in which trabeculae are rarely found, by cords of adenoid tissue, 

 to the general mass of lymphoid tissue^) (pi. I. fig. 5; pi. II. fig. 12 

 and 13). Here they branch into smaller and smaller vessels and even- 

 tually form a capillary network. 



In preparations in which the arteries were injected the sinus was 

 engorged with the red mass (pi. II. fig. 12), so that this portion of 

 the gland appeared on section of a uniform red colour, except for 

 the regular interruption of reticulum fibres and phagocytes, which 

 give such sections of the sinus a characteristic network appearance. 

 From the border of the sinus adjoining the lymphoid tissue small 

 vessels or capillaries run into this lymphoid tissue (pi. II. fig. 12 and 

 pi. I. fig. 5 c.a). 



After injection of the veiots, sections of the glands showed very 

 different appearances; in some cases no injection had found its way 

 into the sinuses, though minute capillary networks were picked out 



^) I have not found blood vessels or capillaries lying free in the sinus; they 

 invariably have this sheath of adenoid tissue. 



