THERAPEUTIC USE OF ANTI-SEEA 583 



with salt solution to 1 o.o. In this way » definite reaction may be 

 observed with - 001 c.c. of the homologous serum or even less. Here 

 again zone phenomena, as in the ease of agglutination, are met with. If 

 the anti-serum be heated to a temperature of 75° C. for some time it 

 acquires inhibitory properties, so that when added to a mixture of serum 

 and anti-serum which would otherwise give »• precipitate, this no longer 

 occurs. Some observers consider that this is due to the presence of 

 " precipitoid " in the heated anti-serum ; but the observations of Welsh 

 and Chapman show that this view is not in aecordance with the facts, and 

 indicate that the inhibition is related to a specific solvent action which 

 the heated anti-serum has on the precipitate. They have also shown 

 that the main mass of the precipitate is furnished by the anti-serum 

 (precipitin), and not as. is usually supposed by the protein of the 

 homologous serum thrown down by the precipitin ; this result is of high im- 

 portance in connection with the action of anti-substances in general. The 

 precipitin reaction is specific in the sense explained above. It is always 

 ■most marked towards the serum of the species used in the immunisation ; 

 but while this is so, there may also be a slight reaction towards animals 

 of allied species. An anti- human serum, for example, gives the maximum 

 reaction with human serum, but also a slight reaction with the serum of 

 monkeys, especially of anthropoid apes ; it, however, gives no reaction 

 with the serum of other animals. The precipitin test has thus come to 

 be employed as a means of differentiating human from other bloods. 

 Another interesting phenomenon is what is known as the "deviation of 

 complement," which is produced by the combination of the two substances 

 in the serum and anti-serum respectively. If mixtures be made according 

 to the above method, and then a small quantity of complement, say fresh 

 guinea-pig serum, be added, it will be found that the complement 

 becomes absorbed, as may be shown by subsequently adding »■ test 

 amount of sensitised red blood corpuscles. This deviation phenomenon 

 is even a more delicate reaction than the precipitin test, it being often 

 possible to demonstrate by its use from a tenth to a hundredth of the 

 smallest amount of serum which will give a perceptible precipitate ; it 

 also is specific within the same limits. ' 



Therapeutic Use of Anti-Sera. — As will have been gathered, 

 the chief human diseases treated by anti-sera are diphtheria, 

 tetanus, streptococcus infection, cerebro-spinal fever, pneumonia, 

 dysentery, plague, and snake bite. The methods of application 

 in bacterial infections and the general results have been dealt 

 with in treating of individual diseases. In snake bite the use of 

 antivenenes is limited, for Lamb showed that, if a cobra with 

 full glands bites a man, many times the minimal lethal dose are 

 probably injected. Grave symptoms thus come on so rapidly 

 that usually no opportunity is offered for remedial treatment by 

 the anti-sera. Moreover, as a definite specificity exists between 

 the poison of a particular, snake and its antivenene, unless the 

 appropriate serum is available, little effect will be produced. In 



1 For an account of precipitins, vide Nuttall, "Blood Immunity and 

 Relationships," Cambridge, 1904 ; and of complement deviation, Muir aud 

 Martin, Joum. of Hyg. (1906), vi. p. 265. 



