17 Mittheil. aus d. Embryol. Instit., i., 1877.
On the other hand, while the above reasons go to prove that diphtheria attacks children by preference, there is again an anatomical and physiological condition—to wit, the free slightly acid secretion of the mouth, beginning with the third month—that acts as a hindrance to the frequent occurrence of diphtheria after the third month. A poison or poisonous product of whatever nature can less readily find a hiding-place so long as it can be readily—we might always say must surely be—washed away. During these months of eruptive secretion from the mouth diphtheria, therefore, is not very frequent; thus teething, in the case of diphtheria, cannot be held responsible by mothers fond of diagnosticating dental diseases. In this connection the remark of Krieger ought not to be overlooked, who explains the relative scarcity of the disease in the first year of life by the fact that cumulative influences will produce a great number of cases, and cumulation requires time. Undoubtedly, however, an important etiological consideration is the fact of having had the disease previously. We can cite a host of zymotic diseases the occurrence of which once serves as a protection against future attacks. Not only can no such security be expected after one attack of diphtheria, but, cæteris paribus, the disease shows a preference for those who have survived a previous attack. The statement that only the mild cases, with but slight elevation of temperature and freedom from severe constitutional symptoms, are likely to suffer a relapse is founded on error. True, I have more frequently seen relapses after mild cases—which, fortunately, are in the majority—but the disease has also recurred where originally high fever and an extensive lymphadenitis proved it to be a severe case. Besides, second attacks of membranous croup are also recorded (Guersant, N. F. Gill, Quincke).
As there are individuals, so there are families, which have a predisposition to diseases, as there are others in whom, notwithstanding ample exposure, infection does not easily take place. Yet in the families in which diphtheria is of frequent occurrence it cannot always be attributed to enlarged tonsils and a tendency to pharyngeal or nasal catarrh.
Still, catarrh and the vulnerability of mucous membranes must be considered as a frequent source of diphtheria; children will get numerous relapses often after a nasal or pharyngeal catarrh. Sudden changes in the temperature of the atmosphere or of the surface of the body are therefore dangerous in predisposed persons. And thus it is that while severe epidemics have spared no climate or land known to us, the majority of cases have occurred in winter and spring; in other words, at a time when catarrhal disorders are of most frequent occurrence. In my experience at New York, the first quarter of the year yielded more cases than any other. Still, they are frequent enough in warm seasons. Krieger insists upon the injurious influence of hot summers and dry hot rooms. I do not doubt the correctness of his views, which cannot but be strengthened by the damaging results of our furnace-heating. But the influence of season on the invasion and course of diphtheria is but indirect and conditional, and may be, perhaps, after all, compared with that exerted by filth—a term which is lately used to express all sorts and forms of nastiness, from filthy bodies of men to their clothes, their habits, their food, and the air they breathe, whether polluted by carbonic acid, by excrementitious gases, or by exhalations of sewers.
Cases of diphtheria which are traced to exhalations from sewers (or even to filthy habits of life) are very frequent. Yet typhoid is attributed to the same causes. So is dysentery. Can, then, foul exhalations produce alike diphtheria, typhoid, and dysentery? Do these diseases arise from a common poison? Or is the poison of a treble character, so that a part may give origin to diphtheria, another part to typhoid, a third to dysentery?18 Have we to deal, in such occurrences, with specific influences, or only with a lowering of the standard of health, thereby affording other morbid influences an opportunity to exercise their power? These questions are still involved in darkness, and constitute problems the solution of which still engages the minds of both individual writers and authorities. A report of the Board of Health of Massachusetts, closely adhering to the results of exact observations,19 leaves them doubtful, and the affirmative reports of some modern writers do not bear scrutiny.20
18 In regard to the causal connection of the two latter diseases with sewer exhalations we can be more positive than in regard to the former.
19 Author's Treatise on Diphth., p. 35.
20 M. A. Avery, Med. Jour. and Obst. Rev., Feb., 1882.
Air polluted by bad drainage or leaky sewers has been considered responsible for diphtheria as well as for typhoid fever and dysentery. Not only the impairment of general health, but the direct and unmistakable disease, has been attributed to it. Thus Bayley refers, in the endemic of Bromley,21 the first cases to unventilated sewers and cesspools. School-children multiplied the disease. Thursfield attributes the diphtheria at Ellesmere22 to the accumulation of excrements under the school-room, and to deficient supply of water, which, moreover, was of bad quality. Tripe (like Railton, Bailey, Russell, Bell) accuses sewer gas;23 others polluted waters or bad drainage.24 I have not been convinced, however, that diphtheria can be considered a sewer-gas disease, in the same way as typhoid fever. The deterioration of the general health resulting from the inhalation of foul air is sufficient to explain the outbreak of the individual attack during a prevailing epidemic.
21 Sanit. Record, Aug. 10, 1877.