38 AVENUES OF INFECTION 



highly injurious to infants is without harmful effect on adults. In 

 the fetus digestion is wholly parenteral and it continues to be partially 

 so during the nursing period, and the intestinal walls of infants are 

 more permeable to both formed and unformed substances than are 

 those of the adult. According to von Behring, the great majority of 

 cases of tuberculosis are due to infection from milk in infancy. The 

 bacilli are retained in the lymphatic glands and invade other organs, 

 especially the lungs, later in life. 



Calmette teaches that in every period of life tuberculosis generally 

 enters the body through the intestinal walls where it leaves no lesion 

 and from which it travels to other organs. It has been shown that the 

 tubercle bacillus may pass through the intestinal walls without leaving 

 any recognizable lesion, but it is not so certain that this is the usual 

 port of entry. Even in the adult, the intestine seems to be the most 

 vulnerable point in bacterial invasion. It is the exclusive port of 

 entry for cholera, dysentery and typhoid. The most virulent cholera 

 bacillus injected under the skin in amounts which would fatally infect 

 by the intestine, would be without serious effect. The list of animal 

 infections, which are essentially intestinal, embraces anthrax, chicken 

 cholera, the hemorrhagic septicemias, hog cholera, and mouse typhoid. 



It is a noteworthy fact that in experimental infection by feeding, 

 larger numbers of bacilli must be employed than can possibly be 

 required in natural infection. It has been inferred from this that in 

 natural infection the intestinal conditions must be especially favorable 

 to the multiplication of the organisms. This has led to the assumption 

 that slight intestinal disturbances predispose to typhoid and other 

 intestinal infections. This was carefully investigated by the board 

 which studied typhoid fever among our soldiers in 1898, and was 

 found to be without support. Soldiers, who were frequently on sick 

 report with diagnoses of gastric catarrh, intestinal indigestion, etc., 

 furnished actually a smaller percentage of typhoid fever than those 

 who had not been on sick report for any cause. Moreover, many of 

 the short and intermittent disturbances, under a variety of diagnoses, 

 were found by the Widal test to be typhoid fever. Some have claimed 

 that the normal intestine is not easily traversed by bacteria, but the 

 difficulty in this is to know when the intestnial walls are in a healthy 

 condition and when they may have suffered slight injuries. 



