THE SCIENCE AND ART OF PROTEAL THERAPY 149 



the metamorphosis of fats ; but it is consistent with the above line 

 of reasoning to assume that the lymphocytes also may have a 

 hand in this work. Possibly the relative shares of the two 

 types of leucocytes in dealing with fats may vary indefinitely 

 under diversified conditions. 



A further word must be said about the relation of the various 

 leucocytes to the type of protein represented in the bodies of 

 bacteria. At first glance it may seem that the observed fact that 

 polynuclears deal with bacteria, ingesting them bodily, is incon- 

 sistent with the assumption that the chief work of the polynu- 

 clears is to deal with the partially decompounded protein mole- 

 cule. As to this, however, it will be recalled that the suggestion 

 was made that the so-called "opsonins," the presence of which 

 was found by Wright to determine the activities of the leuco- 

 cytes as ingesters of bacteria, may be enzymes secreted by the 

 mononuclear leucocytes ; but it is perhaps even more important 

 to recall that the proteins of bacteria are probably very different 

 in quality from the proteins of vegetable and animal tissues in 

 general. 



Reference has already been made to the fact that the encase- 

 ment of the bacteria is of a fatty or lipoid character. It has 

 been pointed out by Leathes that it is not the cell-membrane 

 alone of the bacteria that is so constituted, but that the fats enter 

 into its entire structure. He says: "These fatty substances, 

 which form a considerable part of the bodies of tubercle bacilli, 

 not only exhibit a very low iodine value, but offer remarkable 

 resistance to measures that are commonly efficacious in saponi- 

 fying fats. And there are reasons for thinking that the vitality 

 and power of resistance of such organisms is intimately de- 

 pendent upon the properties of the fat in which their bodies are 

 enclosed or with which they are impregnated." 



In dealing with the bodies of pathogenic bacteria, then, the 

 organism is not contending at all exclusively with foreign pro- 

 teins, but with structures in which the protein basis is so in- 

 corporated with fatty matter as to modify the conditions very 

 markedly. Moreover, it is probable that the bacterial protein 

 itself is of a quite different order from the proteins of true 

 plants and of animals. The low plane occupied by bacteria in 

 the organic scale suggests the probability that the bacterial pro- 

 teins have molecules of a relatively simple order, comparable 

 perhaps in their complexity to peptones or proteoses rather than 

 to true proteins. On this assumption, as well as in consideration 

 of the presence of the fat, the recognized capacity of the poly- 

 nuclears to deal v;ith bacteria is entirely consistent with the 

 function ascribed to these leucocytes in the above provisional 

 hypothesis. The instances of observed incapacity of the large 



