610 LECTURE XXVI. 



gland. The increased elimination of nitrogen may be caused in many 

 ways. We shall not be in a position to decide such questions until it has 

 been found possible to isolate the active principles from each of the 

 organs. 



We now turn to two other organs for which a specific function has 

 been suggested. These are the spleen and the thymus. The latter is a 

 temporary organ, being a true organ in the case of man only during infancy. 

 After the child is two or three years old it no longer develops, but slowly 

 and steadily atrophies, and has nearly disappeared by the fifteenth year, 

 though traces of it remain in old age. It can be completely extirpated 

 without causing death. It is, therefore, not to be classed with the 

 organs that are essential to life. Its ablation is said to result in disturb- 

 ances in the general health and in metabolism; but from the data at hand, 

 it is not possible for us to obtain a very clear conception of the func- 

 tions of the thymus gland. Similarly, its anatomical construction is not 

 instructive. 1 



We are almost as much at sea concerning the significance of the spleen 

 in the economy of the animal organism. All sorts of different functions 

 have been ascribed to it. It has been said to influence the activity of the 

 pancreas, an assumption which is not well founded. It has also been 

 assumed that it plays a part in the production and destruction of the 

 red corpuscles, and furthermore that it is able to remove and store up waste 

 material from the blood and lymph. This much is certain, however: the 

 spleen can be extirpated completely without any severe consequences. 

 It would be of course unjustifiable to conclude from this that the spleen is 

 an organ of subordinate importance. Everything depends upon the con- 

 ditions under which the functions of an organ are tested. It is perfectly 

 possible that under certain conditions the absence of the spleen might 

 make itself felt. It may be mentioned, in this connection, that great 

 importance has been ascribed to the spleen in combating disease germs. 

 In the case of infections, the spleen sends out a great number of leucocytes. 

 On the other hand, there are certain indications of the fact that the spleen 

 on account of its anatomical construction is called upon to regulate the 

 composition of the blood so that the cellular elements are kept in such a 

 condition that they are capable of exercising their functions. Abnormal 

 red and white blood-corpuscles are held back and destroyed. It is possible 

 that the proteolytic ferment found in spleen, which has an action upon 

 fibrin, may be active in the breaking down of these discarded elements. 

 On the other hand, the high iron content of the spleen, to which our 

 attention has been called repeatedly, is not necessarily to be regarded as 



1 A. Friedleben: Die Physiologie der Thymusdriise (1858). Cf. J. Aug. Hammar: 

 Pfliiger's Arch. 110, 337 (1905). Rudolf Fischl: Z. exper. Path. Therap. 1, 388 (1904). 



