Diagnostic Animal Inoculation. 573 



the true tubercle bacilli there exist certain points of close relationship 

 which find expression in peculiarities referred to as group reactions. 

 These are, aside from morphological resemblances, as follows : The for- 

 mation of tuberculin-like products in cultures as well as their mutual 

 agglutinating properties when treated with sera from animals that have 

 been treated with tubercle bacilli or other acid-fast bacilli; also their 

 property of immunizing animals against the effects of true tubercle 

 bacilli, though this is true only in a slight degree. These and many 

 others of the above mentioned common characteristics are doubtless 

 indications of a phylogenetic relationship and hence arises the possibility 

 that tubercle bacilli represent acid-fast saprophytes that have become 

 pathogenic in the course of time, or that the latter are tubercle bacilli 

 that have been attenuated through the influence of external agencies. 



In view of the fact that the term pseudo-tuberculosis has already 

 been applied to certain other morbid processes it is suggested that the 

 acid-fast bacilli under discussion be referred to as acid-fast paratubercle 

 bacilli. 



Diagnostic Animal Inoculation. These often give a positive result 

 when the presence of bacilli in material to be examined can not be 

 demonstrated with the microscope on account of their small numbers. 

 The demonstration of the infectiousness of milk, in particular, is fre- 

 quently possible in no other way. In other cases diagnostic inoculations 

 of animals are necessary when a microscopical examination is by itself 

 insufficient to determine beyond question that the suspected tubercle 

 bacilli are genuine. 



With a diagnostic inoculation as a basis the diagnosis of tuberculosis 

 is justifiable only when true tubercles (in a histologic sense) have been 

 demonstrated in the inoculated animal or when tuberculous processes 

 have spread from the point of infection to a neighboring lymph gland 

 and to internal organs, liver, spleen, lungs (see above: Pathogenic 

 action of acid- fast paratubercle bacilli) . 



The guinea pig is, above all, adapted for this purpose. It is so 

 extremely susceptible to tuberculosis that negative results from the 

 inoculation of suspected material may, in practice, be looked upon as 

 positive evidence that the material was free from tubercle bacilli. This 

 does not, of course, exclude the possibility that material taken from 

 the same animal at another time may contain the bacilli. 



If the probability of contamination is excluded (specially drawn milk, pus 

 from a closed abscess, tissue juices from internal lymph glands) the material may 

 be injected into the peritoneal cavity without further preparation, or after being 

 merely diluted with water. However, if contamination is probable, or suspected 

 (nasal discharge, bronchial or ulcer secretions), it is advisable to inject a small 

 quantity subcutaneously in the abdomen or on the inner surface of the thigh or 

 into the muscles of the latter. In such cases the foreign bacteria will cause a local 

 inflammation resulting in an abscess which will break and discharge its contents 

 to the exterior and if tubercle bacilli were also present the characteristic patho- 

 logical changes will develop as usual. (According to Ostertag the intramuscular 

 method is just as reliable as the intraperitoneal but preferable to the latter because 

 results are obtained quicker. Laurier recommends intramammary inoculation.) 



In from 15 to 20 days after the intraperitoneal injection of virulent material 

 the peritoneum, spleen, liver and lymph glands contain tubercles and the liver 

 which assumes a mottled appearance undergoes fatty degeneration. After subcutane- 

 ous inoculation an ulcer, which has little or no tendency to heal, develops at the point 

 of inoculation; simultaneously with the development of the ulcer the neighboring 

 lymph glands become enlarged, and later on the process spreads to the internal 

 organs, especially the peritoneum, liver and spleen, and in these numerous tubercles 

 may be found from the 25th to the 30th day after inoculation. After intramuscular 

 inoculations the neighboring lymph glands may be recognized (frequently as early 



