Conclusions 409 



keeping. Fluid antisera, sealed in bulbs and kept cold and in the dark, 

 may at times gi\Q good reactions after 6 to 14 months. Putrefaction of 

 serum, or antiserum, does not affect the production of a specific 

 precipitum. 



There is evidence that the precipitin-content of the serum in corpure 

 undergoes fluctuations during immunization, corresponding to those 

 observed in animals under toxin-treatment. The precipitins begin to 

 disappear about 1 month after treatment has ceased. The precipitins 

 disappear from the blood of animals which have undergone prolonged 

 treatment, the animals having become immune. The precipitins may 

 be present in the humor aqueus, and are transmitted to the offspring in 

 utero, whilst they are absent from the urine. The precipitin and 

 precipitable substance may co-exist in corpore, no precipitation ap- 

 parently occurring in the body. The presence of foreign precipitable 

 substance in an animal's serum may be readily demonstrated by means 

 of an antiserum for the foreign substance. No explanation can as 

 yet be given of the marked leucocytosis after injection of a foreign 

 albumin into an animal which has been rendered more or less immune 

 to the albumin. The seat of origin of the precipitins is unknown. 



The more powerful an antiserum is, the greater is its sphere of action 

 on other bloods. The degree and rate of blood reaction appear to offer 

 an index of the degree of blood-relationship ; in other words, closely 

 related bloods react more powerfully (more precipitum) and more 

 rapidly than do distantly related bloods, provided the latter react at all. 

 The interaction of a precipitin with its homologous blood dilution is not 

 impeded through non-homologous bloods of various kinds being present 

 in the blood-dilution in mixture. The amount of reaction may be 

 expressed in terms of the volumetric measurement of the precipitum 

 produced by mixing known quantities of the interacting substances. 

 An antiserum acts upon a higher dilution of homologous than of non- 

 homologous substance. The strength of an antiserum may be expressed 

 either in terms of precipitum-volume, or, by giving the highest dilution 

 of blood with which it reacts, the quantities of the interacting substances 

 being stated. The amount of I'eaction may be affected by altered blood- 

 concentration in disease, possibly also by the variation in the alkalinity 

 of the blood in disease, or even in health. There is evidence of iso- 

 precipitins, autoprecipitins, and antiprecipitins being artificially formed 

 in the bodies of treated animals. Certain normal sera may contain 

 precipitins, but these do not possess a specific character. 



The bacterio-precipitins appear to be distinct from the others 



