66 PREPARATION OF ANTITOXIN ON A LARGE SCALE 



assistant pinches the indiarubber tube and places the outflow tube 

 in a second pot. The outer cover is replaced on the first pot, 

 which is removed to a warm place to clot. The process is repeated 

 until twelve or fourteen pots have been filled. 



Horse's blood coagulates slowly, and a well-marked buffy coat is 

 formed. In twenty-four hours this will have contracted, and 

 much of the serum will be squeezed out. In order to draw this 

 off use is made of a wash -bottle, the short tube of which is con- 

 nected with a water-pump, such as is used for filters, by which 

 a partial vacuum can be maintained. The long tube is connected 

 to a piece of indiarubber tubing terminating in a length of glass 

 tubing. A jam-pot is opened by half reflecting the outer cover 

 and lifting the triangular strip cut in the inner one, and the glass 

 tube is inserted. Air is now sucked out of the wash-bottle by 

 turning the tap which puts it into communication with the suction- 

 pump, and the serum siphons over. When all the serum has been 

 abstracted a second jar is treated in the same way, the parchment 

 cover of the first being replaced, and the process is continued with 

 all the jars. In twenty-four hours more serum will have appeared, 

 and the process is repeated, and a small amount may often be 

 obtained on the third day. In this way the total yield of anti- 

 toxin is usually nearly 50 per cent, of the total volume of blood 

 (4i to 5 litres). 



The antitoxin thus obtained is usually sterile, the most careful 

 precautions being taken to prevent contamination. Carbolic acid 

 (0-3 per cent.), or trikresol (0-3 per cent.), or a mixture of the two, 

 must now be added to preserve it. It is then filtered through 

 a Berkefeld filter (not a Chamberland filter, through which it 

 passes with great difficulty, if at all), a low pressure only being 

 used, and finally tested for sterility by means of cultures, and for 

 the presence of toxins by the injection of large (10 c.c. or more) 

 amounts into normal guinea-pigs. 



A specimen is taken at the time of the bleeding, and this is 

 tested for antitoxic value in the manner to be described subse- 

 quently. The results of this testing will give the amount necessary 

 to obtain the required dose, and this amount is placed in sterile 

 tubes or bottles ready for use. In most cases mixtures are made, 

 antitoxin of low potency being mixed with more powerful sera in 

 order to obtain the requisite dose in a given volume of serum. 

 An ingenious machine is used by which the tubes or bottles are 

 filled automatically with the antitoxin in the required amounts. 



