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SCIENCE 



[N. S. Vol. XLIV. No. 1126 



A scientific discovery may be considered 

 worth while if it merely gratifies intellec- 

 tual curiosity and adds an apparently insig- 

 nificant support to a structure, the totality 

 of which makes for human knowledge and 

 welfare. It is a characteristic of the med- 

 ical sciences in general, and of bacteriology 

 in particular, that the discovery of new 

 principles has led very rapidly to practical 

 results of the greatest significance to man- 

 kind. In no instance is this characteristic 

 more strikingly true than in the study of 

 typhoid fever. The study of B. typhosus 

 as the single and essential cause of typhoid 

 fever led rather rapidly to important ad- 

 vances in the prevention and cure of the 

 disease. 



I have already referred to the valuable 

 suggestions of Budd and Murchison that 

 the potential danger of contagion in typhoid 

 fever lies in the excreta from patients. In 

 common with all empirical results arrived 

 at by retroactive judgment between cause 

 and effect, these suggestions were only 

 partly convincing and led to only partial 

 avoidance of the danger. Witness, for ex- 

 ample the obstinate assertion of Petten- 

 koffer, the great hygienist, who insisted 

 that the contagion in this disease must pass 

 through a ripening stage in the earth, and 

 that its spread is dependent on the level of 

 ground water. The demonstration that the 

 typhoid bacillus was not only the cause of 

 the disease, but that it is present in the 

 stools and urine of typhoid patients, at 

 once led to more logical and far-reaching 

 avoidance of these sources of contagion. It 

 was accepted not only that typhoid patients 

 are a source of possible danger, but it was 

 soon suggested that even after their re- 

 covery they might continue to retain the 

 germs of the disease in their urinary bladder 

 or intestines (Horton-Smith, 1900; Koch, 

 1902). This led, at Koch's suggestion, to a 

 systematic investigation of the stools of re- 



covered cases of typhoid fever in certain 

 parts of Germany where the disease was 

 particularly prevalent, and showed that 

 four per cent, of all recovered cases remain 

 "carriers" of B. typhosus for varying 

 lengths of time, some of them for years. In 

 connection with this study Drigalski made 

 the important observation that a few indi- 

 viduals may harbor the typhoid bacillus in 

 their intestines without ever having suffered 

 from the disease, "healthy carriers" as they 

 are called. Repeated observations in all 

 parts of the world have shown that through 

 contamination of foodstuffs, these carriers 

 may produce not only a chronologically ex- 

 tended series of cases, but actual acute epi- 

 demics. The obvious remedy consists in 

 detecting the innocent but dangerous indi- 

 vidual and isolating or curing him. 



Food contamination occurs not only in its 

 preparation by carriers, but sometimes 

 through transfer of the bacteria by flies, as 

 has been shown to be the case particularly 

 in asylums and prisons where excreta have 

 been left exposed in the neighborhood of 

 kitchens. Reed, Vaughan and Shakespeare 

 have particularly emphasized this danger 

 of fly transmission in their careful study of 

 the devastating effect of the disease among 

 our troops in the Spanish-American war. 

 Evidence of this sort has led to an apprecia- 

 tion of the necessity of proper, protected 

 latrines which can be rapidly built even in 

 temporary camps. 



These and other real contributions toward 

 the prevention of the spread of typhoid 

 fever have been made by pure bacteriology. 

 Let us now consider what the sister science 

 of immunology has accomplished. I have 

 only suggested how much the demonstra- 

 tion of the typhoid bacillus in the blood or 

 stools of a suspected case of typhoid may 

 aid in diagnosis of the disease. As a matter 

 of fact no diagnosis is complete or indeed 

 certain without such examination. An even 



