MECHANISM OF PROTEIN HYDROLYSIS AND IMMUNIZATION 37 



cise mutual relations of the different types of leucocytes. There 

 is a general impression that these fall into two groups, one of 

 myelytic origin and the other of lymphatic origin. In the former 

 group are the basophiles, the eosinophiles, the large mononuclears, 

 and the neutrophiles. In the latter group are the lymphocytes. 

 Whether or not the lymphocytes should be divided into small 

 and large, as two different classes, is a matter regarding which 

 the authorities are not agreed. Also the question of the precise 

 origin and functions of the large monocytes is by no means 

 settled. Ehrlich regarded them as the forms which, developing 

 through a transitional stage, became transmuted to polynuclears. 

 But it does not appear that there is any positive evidence in sub- 

 stantiation of this view. 



Furthermore, it has been disputed as to whether the large 

 lymphocytes are the parent forms of which the small lympho- 

 cytes are the daughter cells; or whether, on the other hand, the 

 small lymphocyte grows and develops into a large lymphocyte. 



Meantime, it does not appear that any one has given close 

 study to the question as to the precise material out of which 

 the bodies of the various leucocytes are developed, nor as to the 

 specific distribution of their protein bodies after disintegration. 

 It has been observed that there may be deviation of two thousand 

 or three thousand leucocytes to the cubic millimeter under nor- 

 mal conditions in the course of a day. Reinart, for example, gives 

 the average number of leucocytes at six o'clock in the morning as 

 5,125; and the average at 4 P.M. as 8,262. If we may accept 

 such a variation as this as typical, it becomes obvious that the 

 growth and disintegration of three thousand leucocytes to the 

 cubic millimeter as a normal process during a period of twenty- 

 four hours involves a cycle of protein metabolism that is highly 

 significant. A very interesting question and a question of great 

 importance arises as to whether the transmutation of raw mate- 

 rials, so to speak (with amino-acids for the ultimate building 

 stones), through which the bodies of the leucocytes are built up 

 takes place only in the mother organs of bone marrow and lymph 

 nodes, or whether the free leucocytes in the blood stream con- 

 tinue to grow and develop, taking to themselves food pabulum, 

 and passing through stages of individual development that may 

 be properly spoken of as juvinility, maturity, and old age. 



The well-known fact that the larger types of leucocytes exer- 

 cise a phagocytic function, seeming to feed on the bodies of 

 bacteria, gives strong support to the supposition that these cells 

 are capable of ingesting protein pabulum and converting it into 

 material for the increment of their own particular protein sub- 

 stance. It is believed by some observers that the granular struc- 

 ture of the leucocytes commonly spoken of as myelocytic (that 



