66 The Preci'pit{7is : Methods 



doubt but that in certain cases such reactions have led investigators 

 astray. (See further pp. 76 — 79.) 



The tests here recorded were carried out with pure antisera, upon 

 bloods which proved soluble in salt solution. In some cases, through 

 misadventure, microorganisms developed in the sealed tubes of antiserum. 

 Where this occurred the serum was centrifugalised, being cleared in 

 this manner in some cases, not in others. The microorganisms collected 

 in the drawn-out lower portion of the tube (Fig. 3), and when the latter 

 had to be opened the glass was cut above the part including the 

 deposit. It is a remarkable fact that even putrid antisera continued 

 to produce their special reactions, in some cases at any rate, without 

 any apparent decrease. The microorganisms present included bacilli, 

 micrococci and moulds of various kinds, the species not having been 

 determined from lack of time. It appeared to me to be a matter 

 of some interest to study the effects of different germs by cultivating 

 these in antisera^ In the paper by Nuttall and Dinkelspiel (11, V. 

 1901) it was noted that human blood which had undergone stinking 

 putrefaction for two months still gave a full reaction on the addition 

 of anti-human serum, this blood not reacting to other antisera. 

 This observation has been confirmed by the independent investiga- 

 tions of Uhlenhuth (25 April, 1901) and Ziemke (27 June, 1901) 

 on putrid bloods. Certain putrefactive processes do not therefore seem 

 to affect the bodies in antiserum and serum in so far as the amount of 

 precipitum they produce by their interaction is concerned. 



In making the tests described below square-cut pieces of filter-paper, 

 of fairly uniform size, saturated with blood and dried, were placed in 

 a definite quantity of normal salt solution. As I have noted elsewhere 

 (July 1901, p. 378) blood and serum which is dried on glass plates only 

 dissolves slowly and frequently gives clouded solutions. On the other 

 hand, the filter-paper method, as I have shown, rapidly yields clear 

 serum solutions, the fibres of the filter-paper retaining the fine particles 

 which would otherwise go into suspension. To clear such clouded 

 solutions Uhlenhuth has resorted to the tedious method of filtering 

 them through Chamberland filters. I have found this to be usually 

 unnecessary. Where I have to deal with a clouded blood, I drop some 

 of it on to filter-paper and place the paper for half-an-hour or so in the 

 thermostat to dry, after which I place it in saline and usually obtain 

 a clear solution without more ado. 



Where serum only is present on the filter-paper the solution may be 



^ See the experiments by Graham-Smith and Sanger (1903) given on pp. 119 — 122. 



