REVIEW — TEOnCAL MEDICINE, ETC. 213 



reaction after an interval of 31 clays between the two operations, but in normal, healthy Tuberculosis 

 persons this reaction did not occur after an interval greater than eight days between the —contimml 

 two operations. 



The role that flies play in relation to the transmission of tuberculosis has been 

 worked out by Andre'* of Lyons. He observed that flies which have had access to 

 tuberculous sputum retain the tubercle bacilli in their digestive tubes for several days, and 

 that the tubercle bacilli multiply there more rapidly than in cultures. Furthermore, he 

 observed that the tubercle bacilli were present in abundance in the droppings of the flies and 

 therefore it is obvious that the fly can act as a vehicle for tubercle by depositing its infected 

 droppings on articles of food. Although the fly is only a simple vehicle and does not itself 

 become tuberculous, its digestive fluids appear to be a favourable medium for the cultivation 

 of the tubercle bacilli, and if so, why not for other pathogenic organisms? These 

 experiments lend added importance to the necessity for the disinfection and destruction of 

 tuberculous sputa. In connection with tuberculous sputa, mention may be made of a paper 

 by Ziesche,^ whose observations on the disinfection of droplets by coughing consumptives are 

 of interest. He found that the droplets originating in the oral mucosa were free from 

 tubercle bacilli, while in the drops originating from the bronchial mucosa bacilli were usually 

 found, often in great quantities. The droplets were collected on a glass screen 18 c.c. square, 

 and 40 c.c. to 80 c.c. distant from the patient. In 80 per cent, of the cases no bacilli, or less 

 than 400 bacilli, were present ; in the remaining 20 per cent, between 400 and 20,000 tubercle 

 bacilli were found. He concludes by saying that drop infection would not occur if one 

 remained in the presence of a consumptive person only for a short time, but a constant 

 and close intercourse, as between mother and child, often leads to infection. 



Eeference may be made to the channels of infection of tuberculosis. For man the 

 opportunities for infection vary according to customs and habits. Under certain circum- 

 stances children may be infected through the intestinal tract when consuming tuberculous 

 milk or butter, or by putting their fingers tainted with tuberculous sputa into their mouths. 



This theory of the intestinal channel of infection first received support from Behring. 

 A very extensive source of infection is represented by the frequently large quantities of 

 droplets containing tuberculous bacilli which are coughed out by the tuberculous patient 

 and which mix with the atmosphere of his immediate surroundings. This is the most 

 dangerous mode of transmission, as infection occurs even from the smallest quantity of 

 bacilli, and, as the opportunities for this method of infection are so common, it is certain 

 that by far the largest number of cases of human tuberculosis are the result of the 

 inhalation of the tubercle bacilli ejected in the sputum droplets of tuberculous patients. 



Dr. Eibbert, of Bonn, in a paper read at the International Congress of Hygiene in 

 Berlin, states that intestinal infection does not play any great part as compared with 

 aerogenic infection, and that tuberculosis of the bronchial glands can only be of aerogenic 

 origin. Eavenel of Philadelphia, on the other hand, says that the alimentary tract is a 

 frequent portal of entry for the tubercle bacillus. 



In this connection Calmette's' conclusions require notice : — 



1. There is considerable difSculty in experimentally showing the respiratory method of tuberculous infection. 



2. In natural contagion dry dust containing the tubercle baoiUus does not play any r61e in infection. 



3. Ingestion of virulent tuberculous material or cultures in fine liquid emulsion constantly succeeds in 

 producing tuberculosis in all susceptible animals. The bacilli can be absorbed by the intestinal mucous membrane 

 without producing any lesion. They arc carried by the chyle to the mesenteric lymph glands. Thence they are 

 carried by the macrophages along the thoracic duct to the hlaaH circulatory system. The cipillaries of the lung 

 are most exposed to infection, and this explains the frequency of pulmonary infection. 



4. The course of tuberculous infection is the more rapid and grave according to the number of virulent 

 bacilli absorbed, and greater when the absorptions occur at frequent intervals. 



5. A closed tuberculous lesion resulting from a single infection is capable of ciu-e, with a resulting immunity. 



6. Inherited tuberculosis is rare, results always from infection in utero, and is of little importance as a factor 

 in the origin of tuberculosis. 



7. The notion of tuberculous soil or predisposition should be abandoned, as it has been shown by experiment 

 that infection is always possible in susceptible animals, and it bears a direct relation to the number of virulent 

 bacilli absorbed and to the frequency of the inoculation. 



1 Andre, L. (November, 1906). O.R. Soe. Med. Hop. de Lyon. 

 ' Ziesche, H. (1907). Zeil. ftir Hygiene, Vol. 57, No. 1, p. 50. 



■' Calmette, A. (September, 1907), " Les voies norm.ales de penetration du virus tuberculeux dans I'organisme." 

 BuU. de rinstitut Pasimir. 



* iVrticle not consulted in the original. 



