542 MICROBIOLOGY OF THE DISEASES OF MAN AND ANIMALS. 



before stated, animals may be sensitized and intoxicated by the pro- 

 teins of bacterial cells the same way that they are to proteins such as 

 egg-white. This sensitization is also transferred in utero to the first 

 generation; that is, a mother may be sensitized, convey the sensitiz- 

 ing substances to her young while in the uterus, and when these off- 

 spring are subsequently injected after birth with the same protein they 

 may be intoxicated or killed. 



PREDISPOSITION AND NON-INHERITANCE or INFECTIOUS DISEASES. 

 There is, probably, no such thing as a truly inherited infectious disease. 

 This point has been debated and discussed for a great many years and 

 the above conclusion has been reached by the majority of investigators. 

 By inheritance is meant the transference of a property or, in this instance, 

 a pathogenic microorganism by the nuclear substance of either the sper- 

 matozoon or the ovum. It is only the nuclear substances which combine 

 to form the new individual. It is true among certain of the lower animals, 

 such as the fowls and some insects, that microorganisms are carried 

 within the egg, but in these cases the eggs are quite different in structure 

 from the human or mammalian ovum, the egg is composed largely of 

 yolk-furnishing food and ample opportunity for growth, while the mam- 

 malian ovum contains no yolk. Such instances should be referred to 

 as germ-cell transmission, not inheritance. If the microorganisms were 

 present they would be immediately incorporated within the new develop- 

 ing embryo. If the microorganism ever did find its way into the human 

 or mammalian germ cells it would be doubtless a mechanical impossibility 

 for the cells of the embryo to divide and multiply in proper manner. 

 Such pathogens would rapidly destroy the developing cells in the embryo. 

 It is true that the offspring of certain individuals are born diseased. 

 For example, children are sometimes born with syphilis and tuberculosis. 

 At first thought it might seem that this is inheritance but on careful 

 analysis it will be found that the mother is either syphilitic or tuberculous. 

 Furthermore, the locus of the infection is most frequently in the uterus 

 and the microorganisms are transferred to the unborn offspring by means 

 of the foetal circulation. This condition is what is known as antenatal 

 acquirement, it is not heredity. It is impossible for the male to commu- 

 nicate any disease to the offspring unless the female is first infected. 

 Ante- or prenatal acquirement may then be recognized. What can 

 be said in regard to the predisposition to a definite infectious disease? 

 There is a question as to whether true predisposition does exist. Many 



