A fairly good comparison can he drawn between measles and syphi lis on the one hand, and scarlet fever and tuberculosis on the other. Infection to the former is governed by the very slight power of resistance to the contagium while outside the body and the high susceptibility of mat; by the latter, by the high resistance to the exciting cause exerted by a disposition less susceptible.
We have just seen 11011" nearly every acute disease leaves behind it an especial immunity. It is most surprising, then, believing as NV(' (10 that this immunity depends on the presence of an especial material ill the blood (a immoral immunity, or cellular immunit v of the Organism not clearly understood), that the eh" shows a tendency to catch the disease against which its parents have already acquired immunity. The child inherits peculiarities of race and species as of the individual parent. Why then are the powers of immunity not also inherited? We know that its parents are immune, but notwithstanding this, nearly every child readily catches scarlet fever and measles. The answer to this question is readily wade by deduction and is of importance to the far weightier questions of transmitted and inherited disease, as well as to that of inherited predisposition.
At the outset, we must accept the fact that the generating cells of the father and mother contain not only the characteristics of the species, race, and family, but the individual peculiarities of the parents. as well. If all the characteristics of the father and mother are present in the fattus,—a product of the sexual cells in the process of generation,— and if all these peculiarities, dependent on the definite arrangement of cell protoplasms, have been transmitted to each imlividual cell of the child by the assimilation of nourishment, then it is conceivalde that the child must. resemble the parents, even in their individual characteristics. According to this, every characteristic of the parent should be trans mitted, and the child should thus possess an immunity through that of its parent, i.e., against scarlet fever. This power, however, is assumed only by the leucocyte, for, as mentioned above, this is the only cell which reacts to a disease. This explains how the human body especially provides protection against the transmission of acquired diseases. Most of the bacteria, and especially their toxins. react with the leucocytes (as seen in the Introduction). The spermatozoon and the ovum are not affected, as they never come into contact with the other cells, and so their protoplasmic structure is unable to assume a special immunity, and it is therefore impossible for the germinating, cells to give the organism (i.e., the child) immunity.
The law that only those characteristics can be transmitted from the parent to the child, which are somehow contained in the germinating cells, is of much importance to our study of pathogenesis and pathology. The idea so clearly explained by Martius strengthens this assertion. He says, in a few words, that there is absolutely no transference of a disease from a parent to a child. Disposition or tendency for a disease is the only thing winch can be transmitted from the parents. This tendency or susceptibility has its foundation in the definite composition of the cellular protoplasm of the human being and so must be present in the cells of germination as well. While susceptibility for a disease can be inherited, the disease itself can never be, for the disease is a fact, not a characteristic or a condition. Disease is easily transmitted from the mother to the child, but it can never be inherited as such.
The same thing may be said of immunity: it can never be inherited, but only transferred from the mother to the child. There are many in stances in experimental pathology in support of this fact. Immunity depends therefore on a transfer of some antibody from the blood of the mother into that of the child,—a passive immunity, produced by the protective qualities of the mother-blood. It is always a and never a cellular immunity.
Since acquired immunity against certain infectious diseases depends not only on an increased resistance of the cells, but also on the presence of certain protective materials in the blood, we can easily imagine that the newborn infant in the first weeks of life possesses an immunity against diseases already experienced by the mother. Perhaps this fact explains why babies in the first weeks of life do not catch measles, scar let fever, whooping-cough, or chicken-pox. Just so far as immunity is "in-born" and not inherited, are there inherited diseases. We can speak of "innate," or, still better, "intra-uterine" disease, but it is nonsense to speak of "inherited" syphilis. Let us here speak of the so-called "inherited syphilis" there being no syphilitic disease of the mother; by which we mean that the child is syphilitic, while the mother, show ing no signs of the disease, is assumed to be free from it, and the child is supposed to "inherit" the taint. This old and improbable idea, depending on the just as improbable hypothesis of germinal infection, has been very energetically fought in the last few years by Matzenatter. This writer has concluded, from the most logical reasoning and from clinical observations, that there is absolutely no syphilis in the child without there being syphilis in the mother.