550 PHYSIOLOGY" CHAP. 



development (Fuuke and Kolliker). In adult animals, too, after 

 repeated bleedings, Bizzozero and Salvioli noted the appearance 

 of haematoblasts, which are absent under ordinary conditions 

 (Neumann). 



In view of these facts, and of what has been stated in regard to 

 the functions of bone marrow, we cannot doubt that the spleen is a 

 haemopoietic and haemolytic organ. Its haeniopoietic function, 

 as demonstrated by the presence of the erythroblasts, seems to be 

 very active during intra- uterine life, when the bone marrow 

 contains the fewest number of nucleated red corpuscles : it is 

 greatly reduced in the first period of extra-uterine life, when the 

 haemopoietic function of bone marrow increases ; it is abolished in 

 adults, in whom bone marrow functions in full activity ; lastly, it 

 recurs in adults under circumstances in which the body requires a 

 hurried neo-formation of the cytological elements of the blood. 



That the spleen is not an effective haemopoietic organ in adult 

 animals has been conclusively demonstrated by the recent work of 

 Paton, Gulland, and Fowler (1902) on dogs, cats, and rabbits. 



These authors employed four different methods of research : () 

 comparison of the number of blood -corpuscles present in the splenic 

 artery or carotid with the number of corpuscles pi'esent in the 

 splenic vein ; (&) determination of the effects on the blood- 

 corpuscles of extirpation of the spleen ; (c) measurement of the 

 time it takes in normal and a-splenic animals to regain the normal 

 mass of corpuscles either after haemorrhage or after the action of 

 haemolytic agents ; ((/) study of the action on haematopoiesis 

 of injections of splenic extract. The following results were 

 obtained : 



In dogs and cats no difference was observed either in the. 

 number or character of the erythrocytes in the blood that goes to 

 the spleen, as compared with the blood that flows out from the 

 spleen. It appears, however, that there is a slight reduction in the 

 number of the leucocytes, more particularly in that of the poly- 

 nucleated. 



Extirpation of the spleen in dogs, cats, and rabbits has no 

 apparent effect on the number of erythrocytes, nor upon the protein 

 components of the blood plasma (at least in dogs). There appears, 

 however, to be a slight reduction of the eosinophile leucocytes. 

 After haemorrhage in rabbits, and haemolysis in dogs, the normal 

 number of erythrocytes is restored in the same time, both in the 

 control animals and in those which have lost their spleen. Injection 

 of splenic extract does not produce any augmentation in the 

 number of erythrocytes in the rabbit,, but they do increase, on the 

 contrary, after injection of extract of red bone marrow. 



From the above data the authors conclude that they have not 

 established any fact to prove that the spleen possesses a haemo- 

 poietic function. 



