August 23, 19 17] 



NATURE 



515 



may be due to some chemical substance contributed 

 by the pus to the serum or to something special 

 in the character of the bacteria implanted. This 

 point we can clear up as follows. We go 

 back to our very septic »vound. We clean it 

 out carefully by syringing. That leaves us with 

 a wound cavity clean but still abundantly in- 

 fected. We then take the little cupping apparatus 

 which is shown in Fig. 3. We apply it to the walls 

 of the wound, using light pressure. Then, puncturing 

 the attached rubber tube with the needle of a hypo- 

 dermic syringe, we withdraw the contained air, and 

 lea\e our lymph leech in situ adhering bv negative 

 pressure until the time for redressing the wound comes 

 round. When we now go back to our wound we find 

 there two quite different discharges. We have in the 

 general cavity of the wound a thick pus containing 

 many broken-down leucocytes and pullulating with all 

 sorts of microbes. In the bodv of the Ivmph leech we 

 have a nearly clear lymph containing well-preserved 

 leucocytes and only a very few staphylococci and 

 streptococci. Since we had on ever>- part of the walls 

 precisely the same amount and kind of bacterial infec- 

 tion, and since we are in each case dealing "with the 

 self-same lymph and leucocytes, this difference of re- 

 sults is imputable, not to our having in the Ivmph 

 leech a different bacterial implantation, but to the 

 negative pressure having furnished a larger proportion 

 of blood fluids. 



Fig. 



-Lymph leech in position, showing technique for exhausting the air. 



But with this the problem is, asvou see, onlv in- 

 completely resolved. We have learried that the' cor- 

 ruption of the lymph is not determined bv the nature 

 of the bacterial implantation; we have reason to think 

 it is hindered by a larger afflux of lymph ; and it looks 

 as if it might have something to do with the break- 

 ing down of the leucocytes. But we have not vet put 

 our finger upon the particular element that takes awav 

 from the serum its power of inhibiting microbi'c 

 growth, and converts it into a congenial pabulum for 

 all manner of micro-organisms. 



Let me in this connection invite vou to consider — for 

 that may perhaps put us on the path for the solution 

 of our problem— a scheme of classification of the albu- 

 minous substances. I would propose to classifv them 

 from the point of view of their capacitv to furnish 

 pabulum for microbes, and to distinguish "three classes 

 of albuminous substances. First would come digested 

 albumens. It is familiar matter that these furnish 

 very congenial pabulum for microbes. In the form of 

 peptone we use them for all our artificial cultures. A 

 second category of albumens would be native albu- 

 mens. Muscle, milk, and eggs furnish such albumens. 

 These are not like digested albumens, directlv assimil- 

 able. Before they can be assimilated, whether bv our- 

 selves or by microbes, thev must be broken down into 

 simpler elements by digestion. To that end we, and a 

 certain number of microbes also, are furnished with 

 digestive ferments. There is yet a third class of albu- 

 NO. 2495, VOL. 99] 



mens. I would venture to call these defended or pro- 

 tected albumens. These cannot, like the digested 

 albumens, be directly assimilated. Nor can they, like 

 the native albumens, be directly digested. They are 

 specially defended against the attack of digestive fer- 

 ments. The albumens of the serum fall into this class 

 of ■■ defended albumens." It is well known with re- 

 spect to serum that it has an antlzymotic, and in par- 

 ticular an antitrjptic, power — a power of neutralising, 

 digestive ferments, and in particular trypsin. You 

 will, perhaps, not immediately perceive that the fact 

 that the serum is antitryptic in any way elucidates our 

 problem. But let us take that fact and put it ia 

 another way and then consider. Let us, instead of 

 saying that the serum has an antitryptic property, say 

 that it has a power of preventing its constituent albu- 

 mens being converted into pabulum for microbes, and 

 immediately, as I think, light is projected upon our 

 problem. For once we envisage the facts in that way 

 we are immediately impelled to inquire whether the 

 serum's power of inhibiting bacterial growth may not 

 be due to its power of neutralising digestive feiments,. 

 and whether the corruption of the lymph in the cavity 

 of the wound may not be due to a collapse of its- 

 defence against proteolytic attack. 



That is a point which is very easily settled by direct 

 experiment. And let me now show you what happens^ 

 when we add trypsin to a serum which has been im- 

 planted with microbes. I have here two tubes of a 

 serum implanted two days ago with a minute quantity 

 of pus containing a variety of different microbes. To 

 the one I added trjpsin, the quantity- added being less 

 than that required to neutralise its antitr}ptic power. 

 The other tube of the implanted serum sensed as a 

 control. Both tubes were then placed in the incubator. 

 And you see the difference. The ttypsinised serum is^ 

 turbid with microbic growth. That is, we have here 

 exactly the same result as that obtained in our pvo- 

 sero-culture in those volumes of serum which were cor- 

 rupted by a hea\y implantation of pus; and the same 

 result also as was in the lymph leech experiment ob- 

 tained in the discharges in the wound cavitv. Our 

 control serum has, as you see, remained alniost per- 

 fectly clear. That is exactly the same result as was 

 obtained in our pyo-sero-culture in the distal end of 

 our tube, and again in our lymph leech experiment in 

 the cavity of the lymph leech. 



And the doctrine that the antitryptic power is the 

 protector, and trypsin the corrupter, of the blood fluids 

 wins further support from the following facts : — (i) In 

 every suppurating wound there is, as we shall presently 

 see, a source from which trypsin can be derived. (2) 

 Blood fluids which inhibit microbic growth are stronglv 

 antitryptic; and blood fluids which we find teeming, 

 with microbes are tryptic. (3) Examination of the 

 blood shows that all wounded men have a markedlv 

 increased antitryptic power, and heavily wounded meii 

 (vou saw in our pyo-sero-culture what results from 

 this) on an average a three- or four-fold increased anti- 

 tryptic power. That clearly teaches that the bodv 

 when endangered takes steps to protect itself non- 

 specifically against all microbic infections of the blood 

 fluids. 



The Leucocytes. 



I now pass on to consider the leucocytes and the part 

 they play in the destruction of microbes. You alreadv 

 know with respect to leucocytes that they can emerge 

 from the blood-vessels, burrowing their way out 

 through small pores in the capillar}- walls; that thev 

 make their way to every focus of infection; that thev 

 ingest microbes when these have first been prepared 

 by the action of the blood fluids; and, finallv, 

 that they can, if things go favourably-, digest 

 and dissolve the ingested microbes. There would 

 by consequence in connection with the. leucocvte be 



