i 28 W. F, E. WELDON. 



place iu the case of the metanephros, ■which, originally con- 

 tinuous with the hind end of the Wolffian body, now develops 

 from a separate blastema which bears much the same relation 

 to the hinder end of that structure as the suprarenal blastema 

 does to its anterior end — both modes of origin being probably 

 equally due to the delay which always takes place in the 

 histological diflFerentiation of an organ which is only functional 

 comparatively late in life, and to the need of separating as soon 

 as possible all such temporarily useless structures from the 

 actively functional Wolffian body. 



In the present state of our knowledge as to the function of 

 the suprarenals, it may seem unjustifiable to assume that they 

 have any essential connection with the blood system. At 

 present, the only piece of direct evidence of their possessing 

 any function at all is derived from the phenomena of Addison's 

 disease, which seems, so far as I can learn, to be essentially 

 due to alterations in the blood supply. The constant altera- 

 tions in the behaviour of the red corpuscles^ their refusal to 

 form rouleaux, and the frequent difficulty in obtaining a good 

 clot from the blood of patients suflFering from this disease, are 

 very suggestive. 



An important indication of the probable need for some set 

 of glandular structures in connection with the vascular system 

 is found in the very general presence of such glands among the 

 Invertebrates. It is not too much to say that in every group 

 of Invertebrates in which the vascular system has been at all 

 carefully investigated, glandular appendages to the vessels have 

 been found, which can, from their anatomical relations, have 

 no other function than that of elaborating some of the con- 

 stituents of the blood. Thus, in Chsetopods^ there are very 

 frequently present small csecal diverticula of the great vascular 

 trunks, which are coated with large, nucleated cells, loaded 

 with granules ; these cseca may simply lie loosely along the 

 sides of the vessels, or may be collected into definite glandular 

 masses lying on the floor of the body-cavity. In leeches, 



' See Claparede, "Organisation des Annelides Sedentaires," and 

 Costnovici, "Les Annelides Polycbetes," ' Arch. Zool. Exp.,' viii. 



