We have seen that the rheumatic poison acts on the fibrous and serous tissues of the motor apparatus of the body, and that its action is almost confined to the textures of those joints which enjoy a high degree of functional activity. But these textures are not equally active at all periods of life. In infancy and early life there does not exist the physical strength and stamina necessary for active move ment. After the age of fourteen or fifteen matters change; the child has now reached au age at which work and vigorous exercise begin to form part of his daily life; and when adult life is reached hard work and active exercise are of constant occurrence. This implies the constant possibility of vigorous and free movements of the larger joints, and increased force and activity of the heart's action. It necessitates also a state of preparedness for such action. At any time a call may be made for efforts necessitating such movement and action; and the requisite facilitating and restraining forces must be there to meet the emergency. The period of life at which such ef forts are made is from fifteen to fifty, or thereabouts. This, there fore, represents the period of highest functional activity of those tissues whose duty it is to facilitate and restrain movement. It also represents their period of greatest liability to the action of the rheu matic poison. The period of liability to the action of the rheumatic poison corresponds exactly to the period of functional activity of the tissues specially involved in that disease. The same thing is noted in connection with some of the eruptive fevers. It is specially marked in the case of typhoid. The intestinal glands whose inflammation constitutes the characteristic feature of that disease exist in infancy in but a ntdimentary state. After two or three years they begin to in crease in size and functional activity, and go on increasing till adult life is reached. From that time till middle age they are prominent objects in the intestinal wall. They then begin to diminish in size and functional activity and go on diminishing as age advances till in old age they are practically non-existent, and have ceased to exercise any function. The liability to the action of the typhoid poison is directly as the size and functional activity of these glands. In in fancy and old age the disease is rare. The period of greatest liability to it is from fifteen to thirty-five. All this is adequately explained on the view that these glands are the uidus of the typhoid poison and are essential to its propagation in the system.
In exactly the same way is to be explained the special tendency of the rheumatic poison to affect people between the ages of fifteen and fifty. This is the period of functional activity of those textures whose inflammation constitutes the special lesion of the disease. They form a suitable nidus for the propagation of the rheumatic poison only during their period of functional activity; it is during that period, therefore, that the liability to suffer from rheumatic fever is specially manifested.
4. Hereditary Transmission.—Many diseases are said to run in families—to be transmitted from father to son. And the facts war rant the statement. A gouty parentage gives a liability to gout. The children of plithisical parents are in turn apt to die of the same disease. Rheumatism is also thus inherited.
But when we say that a man inherits a disease from his father, we do not mean to say that lie comes into the world suffering from it, or with its seeds already in him. In the case of gout he may enjoy perfect immunity from it during the greater part of his life and begin to suffer only when forty or fifty years of age. In the case of phthisis perfect health may be enjoyed for twenty years and then the fatal inheritance declare itself. In the case of rheumatism this inheritance seldom declares itself before fifteen, and is generally lost again after fifty.
The son may be born before the father has himself suffered from the malady which he is believed to have transmitted to his offspring. Or the father may even not suffer at all; he may be simply the me dium of transmission to his son of a malady from which his fore fathers had suffered. Evidently it is not the disease itself, but only the family tendency to it which is transmitted. To transmit an actual
disease the father must have its poison in his system when his son is begotten; in which case the child will be born with the malady already developed—as in the case of syphilis. But that is a very different thing from what occurs in the case of rheumatism. What is there transmitted is not the disease but a tendency to it—a greater or less liability to contract it.
This tendency is generally referred to as a constitutional predis position. But to give it a name is to indicate, not to explain its ex istence. What is a constitutional predisposition to rheumatism? Wherein does it consist? And what do we mean when we say that a man has inherited rheumatism from his father? Acute rheumatism consists in inflammation of the fibrous and serous tissues of the motor apparatus. Its poison is a miasmatic organism which is propagated in the system, and finds the nidus requisite to this propagation in those tissues whose inflammation co7istitutes the special lesion of the disease. For the production of acute rheumatism, therefore, two factors are necessary—first, the poison introduced from without; second, that peculiar condition of the tissues of the motor apparatus which imparts to them their spe cial fitness to act as a nidus for this poison. Which of these factors is it that is transmitted? Or is it both? One or both it must be, if we recognize transmission at all. It is certainly not both, for their coexistence in the system at birth would give rise to the disease in the infant. As certainly it is not the first, for a miasmatic poison is essentially one which is received into the system from without, and which gives rise to a disease which is not communicable. It can only be the second ; it can only be that peculiar condition of the tis sues of the motor apparatus which renders them a fitting nidus for the propagation of the rheumatic poison. The difference between a rheumatic and a non-rheumatic subject is that the motor apparatus of the former contains that special ingredient which is requisite to the propagation and action of the rheumatic poison; while that of the latter does not. Between the fibrous tissues of the two men there is no difference that can be detected either by the anatomist or the chemist; but in the one, these tissues afford a nidus for the propaga tion of the rheumatic poison—in the other they do not. In the one the tissues of the motor apparatus contain something which is want ing in those of the other. It is the presence of this something which constitutes the peculiarity of the rheumatic constitution. It is the tendency to the development of this peculiarity which is transmitted from father to son, and makes each generation susceptible to the action of the rheumatic poison. That such a peculiarity should be inherited consists with all that we know of hereditary transmission. There is no reason why internal peculiarities should not be trans mitted as well as external—why a peculiar condition of the brain, of the stomach, of the liver, should not be handed down from father to son as well as a special cast of features, a particular color of hair, a peculiar gait, or a peculiar shape of the limbs. And we know as a fact that certain peculiarities of internal organs are transmitted. Furthermore, there is no reason why peculiarities of individual struc tures should not descend from generation to generation as well as pe culiarities of individual organs; indeed, peculiarity of an entire organ presupposes peculiarity of its individual parts. It consists with all reason that peculiarities of the motor system should be inherited, as well as peculiarities of the nervous, digestive, osseous, and other sys tems of the body. That some peculiar condition of the motor system is handed down in rheumatism we know. That this condition declares itself by a special susceptibility of the tissues of the motor apparatus to the action of the rheumatic poison we also know. But more than this we cannot say; for in this as in all other cases of hereditary transmission we can only indicate, not explain, the fact. So far as the bearing of this fact on the miasmatic theory of rheumatism is con cerned, we can only say that that theory perfectly consists with it.