46 Th. Lewis, 



glands. He has found typical haemal glands in a foetal calf measuring 

 9 inches, which were in diameter from • 5 to • 75 mm. 



As to the first objection brought forward against the view that 

 they are developed from ordinary lymphatic glands, I cannot agree 

 with Drummond in his opinion that hsemal glands have not a very 

 similar distribution to ordinary lymphatic glands. In the Ungulata 

 the two varieties are found together in all situations within the 

 body and chest cavities. In rats the general arrangement is cer- 

 tainly very constant, but so also is the distribution of ordinary 

 lymphatic glands. Further, in the only case in which I have ob- 

 served a renal hœmal gland absent in the rat, it was replaced by a 

 lymphatic gland. 



In a human foetus 5 months old, I have found two small renal 

 glands, which were undoubtedly hsemal glands, though too macerated 

 for histological examination. It has also been noticed, that in rats, 

 the older the rat, the more characteristic is the gland: in the youngest 

 rats, glands containing but a very small proportion of sinus occur, and 

 in still younger ones, or in embryos before birth, structures containing 

 no blood sinuses are often present. In this animal the sinuses seem 

 to appear and develope as the animal grows. ^) 



There is no direct evidence that haemal glands are developed in 

 the individual from ordinary lymphatic glands, though we may con- 

 ceive of their having been phylogenetically so derived. 



XIII. On the structural inter-relationship of the various 

 members of the haemolymph series. 



It is necessary, before entering upon a comparison of the different 

 members of the haemolymph series, that a short description should 

 be given of the structure of the spleen, as it has been interpreted 

 after the examination of a number of specimens. The previous lite- 

 rature on the subject is so extensive, that it cannot here be fully 

 considered. It is only essential to briefly summarize the accounts 



^) In a pup, less than one week old, recently examined, very numerous 

 glands were found. They were present in larger numbers than in the adtilt, and 

 their sinuses appeared larger. They have not yet been histologically examined. 



