CHAPTER 10 

 PATHOLOGY 



1. General. 2. Rat diseases. 3. Toxicology. 4. References to Literature. 



1. General. In the various studies on the pathology of the 

 rat there are, of course, some data, which might be tabulated or 

 charted. It has been thought best, however, to adhere to our 

 general plan of treating in detail the data for the normal animal 

 only and the presentation in this chapter is therefore mainly to a 

 series of references, including those on the Norway as well as the 

 Albino, classified according to the subheads there given. 



Touching the value of the rat for pathological studies the follow- 

 ing citations are given. 



The value of the rat as an experimental animal was impressed upon 

 one of us five years ago when studying, in association with Dr. F. B. 

 Mallory, the lesions produced ■ by a t3^phoid-like organism, Danysz 

 virus, or B. typhi murium. The likeness between these histological 

 changes and those occurring in tvphoid fever in man were striking 

 (Mallory and Ordway, '09). 



The intimate relation of the rat to man, as an intermediary host in 

 certain diseases, the similar omnivorous character of its diet, the natural 

 occurrence and experimental production of morbid conditions similar 

 to those occurring in man make the rat not only an important annual to 

 study in its relation to the public health, as has been done so ably by 

 the United States Public Health and Marine Hospital service, but in its 

 relation to general and special problems of disease, from the physiologi- 

 cal and the chemical, as well as from the anatomical and histological 

 point of view (Ordway and Morris, '13). 



2. Rat diseases. The commonest aihnent is a lung infection, 

 often designated as "rat pneumonia. " Studies on this have been 

 made by Hektoen '16; Tunnicliff '16; Jones '22 and a number of 

 others. 



This disease occurs in the wild Norway as well as in the Albino. 

 It seems less frequent in Albinos allowed to exercise, but is 



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