1 906.] Specificity and Action in Vitro of Gastrotoxin. 431 



matter, but it is not possible to completely free such a solution from 

 protoplasmic granules by cenrtifugalisation alone. The solution is filtered 

 through a Berkefeld filter. The resulting filtrate, which is a perfectly clear 

 solution like water, gives a precipitate with heat, ferrocyanide of potassium, 

 and acetic acid, and other precipitants of proteids. 



The experiment is done in the same way as that described for the 

 agglutination test. The gastrotoxic serum is diluted and placed in a series 

 of test-tubes, and to the contents of each test-tube 05 c.c, or even only 

 two or three drops of the proteid solution, are added. The tubes are placed" 

 in the incubator for four or five hours. Controls of normal rabbit's serum 

 and salt solution are also prepared. 



Precipitation. — At the end of one hour's incubation a fine precipitate has 

 •commenced to form in the solution. This precipitate becomes coarser in 

 appearance, and at the end of about four hours has settled to the bottom of 

 the tube in considerable quantity, forming a deposit. Flakes of precipitate 

 can still be seen floating about in the otherwise perfectly clear supernatant 

 fluid. Under the microscope this precipitate is seen to consist of amorphous- 

 looking masses. If the tubes are placed in the ice-box until the next day 

 the whole of the precipitate will be found to have settled to the bottom, 

 leaving the supernatant fluid perfectly clear. 



As in the case of the agglutination test, I record the result of the 

 experiment both at the end of four or five hours, and also on the following 

 •day, although in this case one can exclude the presence of bacteria, since 

 the tubes have been sterilised and plugged with cotton wool, and the gastric 

 solution filtered. 



The control tube containing normal rabbit's serum, and that containing 

 salt solution, show no precipitate after incubation. It is thus perfectly clear 

 that the gastrotoxic serum acts chemically upon the soluble proteids of the 

 guinea-pig's gastric cells, producing an insoluble compound. This precipitin 

 appears in the serum about the same time as the agglutinin. 



Effects of Heat. — As in the case of the agglutinin, exposure to a tem- 

 perature of 58° to 60° C. for half an hour does not in the least diminish 

 the power of the serum to precipitate the soluble proteid, since precipi- 

 tation occurs in as high a dilution of the heated serum as it does in the 

 unheated serum. 



It is well known that the effects of heat upon the action of precipitins 

 varies considerably ; some are easily affected, whilst others are resistant. 



Action upon Guinea-Pig's Blood Serum. — The experiment is performed in 

 exactly the same manner as described above. The guinea-pig's serum is 

 •diluted 10 or more times, and - 5 c.c. added to 2 c.c. gastrotoxic serum. 

 vol. lxxvii. — b. 2 I 



