274 BACTERIA 



depend upon the point of entrance, as in tetanus. The 

 distant effects of the toxin are due to absorption, but what 

 controls its action it is impossible to say. We only know 

 that we do find pathological conditions in certain organs at 

 a distance and without the presence of bacteria. We have 

 a parallel in the action of drugs; for example, a drug may 

 be given by the mouth and yet produce a rash in some dis- 

 tant part of the body. In the second place (ii.) toxins 

 produce toxic symptoms. Fever and many of the nervous 

 conditions resulting from bacterial action must thus be class- 

 ified. We have, it is true, the chemical symptoms of the 

 pathological tissue change, for example, the large spleen of 

 anthrax or the obstruction from diphtheritic membrane. 

 But, in addition to these, we have general symptoms, as 

 fever, in which after death no tissue change can be formed. 



We may now consider briefly some of the more important 

 types of disease produced by bacteria: 



I. Tuberculosis.^ As far back as 1794 Baillie drew 

 attention to the grey miliary nodules occurring in tuber- 

 culous tissue which gave rise to the term ** tubercles." 

 This preliminary matter was confirmed by Bayle in 18 10. 



In 1834 Laennec described all caseous deposits as ** tuber- 

 cles," insisting upon four varieties: 



(i) Miliary, which were about the size of millet seeds, and 

 in groups; 



(2) Crude, miliary tubercles in yellow masses; 



(3) Granular, similar to the last, but scattered ; 



(4) Encysted, a hard mass of crude tubercle with a fibrous 

 or semi-cartilaginous capsule. 



The tubercle possesses in many cases a special structure, 

 and certain cell-forms frequently occur in it and give it a 

 characteristic appearance. The central part of the tubercle 



'A detailed study of tuberculosis from its pathological and bacteriological 

 aspect will be found in La Tuber culose et son Bacille, pt. i., Straus, Professeur 

 k la Faculte de Medecine de Paris. 



