960 INFLUENCE OF DUCTLESS GLANDS ON METABOLISM. 
in some animals, e.g. rabbits, after extensive blood-letting, nucleated 
erythroblasts, such as those which are found in bone-marrow, occur 
both in the spleen pulp and in the blood of the splenic vein ; and that 
if a spleenless animal is bled, the recovery of the usual percentage of 
red corpuscles is less rapid than in a normal animal. 1 
Whatever may be the nature of its functions in relation to the blood, 
it is certain that the organ is in no way essential to the normal 
nutrition of the body. It is, on the other hand, not at all improbable 
that the main function of the spleen is to serve a mechanical pur- 
pose, answering as a reservoir at certain periods of digestion for the 
blood which has to pass through the portal system ; and the fact that, 
as was first shown by Roy, the spleen normally exhibits regular rhythmic 
contractions and dilatations, seems to point to its exercising an influ- 
ence in assisting the flow of blood through the portal vein, and thus 
through the liver. 2 ,. 
1 Laudenbach, Arch., de physiol. norm, etpath., Paris, 1897, pp. 200, 3Sf>. and S<fe. 
2 The functional connection of the spleen with the vascular system is dealt with in the 
article on " Circulation " in the next volume. Extracts and decoctions of spleen appear to 
have no specific effect, either when injected subcutaneously or intravenously. Nor is any- 
thing known as to any specific functions possessed by the thymus body or by the carotid 
and coccygeal glands. Extracts and decoctions of the thymus appear to have no specific 
effect when injected intravenously (Oliver and Schafer. Journ. Physiol., Cambridge and 
London. 1895, vol. xviii.) or subcutaneously (Vincent, ibid., 1897. vol. xxii.). It has 
been stated that removal of the thymus in frogs is followed by a fatal result (Abelous and 
Billard, Arch, de physiol. norm, et path., Paris, 1896, p. 898), but the statement requires 
corroboration. 
