THE THYROID AND PARATHYROID. 339 



degrees of disintegration, and this is supposed to be brought about 

 by the ameboid cells hitherto described (p. 336). It is stated that 

 in the cells of the spleen hemoglobin is found in different degrees 

 of transformation into other pigments, and a considerable amount 

 of iron is also found in the splenic tissue. It is rather remarkable 

 that if hemoglobin is set free or changed into bile-pigment, one or 

 the other of these substances is not found in the blood of the 

 splenic vein, and yet this is the fact. 



(3) It is a producer of red blood-corpuscles. The formation of 

 red blood -corpuscles does, doubtless, take place during fetal life 

 and for a short time after birth in man, but there is no evidence 

 that this function exists in the human adult, though it does in 

 some animals, as the rabbit. Laudenbach found that in this 

 animal after an extensive hemorrhage nucleated erythroblasts or 

 hematoblasts are found in the splenic pulp and in the blood of the 

 splenic vein, and that if the spleen is removed the number of red 

 corpuscles is diminished, as is also the hemoglobin. In an animal 

 whose spleen has been removed the return of the red corpuscles to 

 their normal number is much delayed. 



(4) It is a producer of uric acid. From the fact that uric acid, 

 as also xanthin, has been found in the spleen, it has been inferred 

 that this is one of its functions. The same is true of lymphoid 

 tissue generally, so that this function cannot be considered as one 

 of the characteristic functions of the spleen. 



(5) It is an enzyme producer. Some experimenters have found 

 that an enzyme is produced by the spleen which when carried by 

 the blood to the pancreas converts the trypsinogen into trypsin. 

 This theory lacks confirmation. 



Schafer sums up his views on the functions of this organ in 

 the following language : " 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 purpose, 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 fi-rst shown 

 by Roy, the spleen normally exhibits regular rhythmic contrac- 

 tions and dilatations, seems to point to its exercising an influence 

 in assisting the flow of blood through the portal vein, and thus 

 through the liver." 



THE THYROID AND PARATHYROID. 



The thyroid gland is also called the thyroid body ; it is situated 

 in front of the trachea or windpipe, and consists of the lobes 

 united by an isthmus. It weighs from 30 to 60 grams, and is 

 larger in females than males, and is said to be larger during men- 

 struation. 



