The Structure and Functions of the hœmolymph Glands and Spleen. 45 



and the remaining' endotlielinm cells again proliferate, liberating a new 

 batch of phagocytes, with the commencement of a new cycle. 



As to the length of the various phases of such a cycle, nothing 

 is definitely known, but it is probable that the stage in which pigment 

 abounds in the sinuses is of longer duration than that in which they 

 are filled with blood. The following statistics seem to indicate that 

 this first stage is approximately double the length of the second. 



No. of rats examined 46. 



,, „ brown renal glands found 59. 



„ „ red renal glands found 32. 



Experimental work in this direction might be done with advantage. 

 For instance a living rat might be opened from time to time and the 

 colour of the organs noticed. Such an experiment would be interesting 

 as furnishing evidence of the time taken by a phagocyte to destroy 

 a blood cell. 



If the above appearances may be construed as indicating a cyclic 

 function of the organs it is probable that they occur throughout all 

 the glands of the body simultaneously, as it is usually found, that if 

 one of the organs has a brown colour, the remainder will also have 

 the same tint. 



XII. Development. 



The development of the haemal glands has as yet received little 

 attention. So far as I know no work has been done in this direction, 

 and a discussion without such investigation is of little value. Vincent 

 and Harrison^) considered that they were modified lymphatic glands, 

 and probably developed from these. Drummond"-^) differed from these 

 observers on two grounds; first that hsemal glands have not the same 

 distribution as ordinary Ij-mphatic glands; and secondly that they are 

 seen at a comparatively early stage in the embryo. He describes 

 the development of the lymphatic system and the adenoid tissue of 

 lymphatic glands, and considers that in the earliest stages the development 

 of the hiemal glands may iiin parallel to that of the true lymphatic 



') Loc. cit. — -) Loc. cit. 



