SOME ASPECTS OF THE IMMUNITY QUESTION. 245 



stances from milk were also made. This fluid was treated 

 with 27-30 per cent, ammonium sulphate, and the first part 

 of the precipitate was collected, dissolved in water, then 

 dialysed, filtered and the filtrate evaporated in vacuo at 35°. 

 1 litre of milk yielded 1 gr. of a yellowish white, transparent 

 substance which contained I4per cent, of ammonium sulphate. 

 This was shown by experiments to possess a value 400-600 

 times that of milk, in the whey of which the protective 

 bodies are found. The later experiments of Brieger and 

 G. Cohn (46) have yielded anti-toxines from milk which 

 possessed an exceedingly high value in rendering animals 

 immune from tetanus. 



Experimental researches on the inheritance of immunity 

 have also been made which seem to show that this inherited 

 character may be transferred to the offspring by the egg or 

 the sperm, and not wholly by the placental blood or the 

 milk of the mother. The researches of G. Tizzoni and G. 

 Cattani (47) show that the young of parents highly immune 

 against tetanus possess a very definite resistance against the 

 artificial production of this disease, though this is less than 

 for the parents. These observers have also attacked the 

 question of the possibility of the direct inheritance of 

 immunity against rabies (48). The method consisted in 

 pairing rabbits, e.g., a resistant father with normal mother, 

 and then testing the individuals of the litter. In three 

 litters the first contained five individuals, and two out 

 of these resisted repeated subdural inoculation of virus, 

 and were still alive after seven months ; two members 

 of the second litter similarly treated were proved re- 

 sistant, while all the third litter succumbed. Out of 

 thirteen individuals only four survived inoculation with 

 virus of great strength, which, without exception, always 

 killed control animals. The conclusions drawn from these 

 observations are that offspring can directly inherit the 

 acquired immunity of the father, and that this by exclusion 

 of other causes can only be due to transmission of the immune 

 condition by the sperm. No peculiarities of the mother 

 play any part in the results of the above experiments, 

 since immunity occurs in individuals of two different litters 



