ALBINO RAT VISCERA, GLANDS, EYEBALLS! WEIGHTS 103 



2,5 



Chart 4 Showing the weight of lungs of the male albino rat according to body 

 weight. The observed weights are represented by 90 male rats. 

 • Observed weight. Calculated weight. 



alter according to the nature of the diet as well as according to 

 other conditions not yet studied. It is interesting to note that 

 a heavy liver is usually associated with a heavy spleen. 



.4. Lungs. The growth of the lungs in weight is represented 

 by the following formula: Weight of lungs = 



0.00471 (Bd. wt. +2) +0.122 log. (Bd. wt. +2) -0.056. 



The constants of the formula were determined from 90 male 

 rats and the relation between the observed and calculated values 

 is shown in chart 4. All evidently pathological cases were elim- 

 inated from the records used. Nevertheless on account of dif- 

 ficulty in deteraiining the infection at an early period, some 

 diseased cases may have been retained. This pulmonary trouble, 

 commonly called 'pneumonia,' seldom appears in rats less than 

 100 grams in body weight, but after this period almost 90 per 

 cent of the ordinary rat population is affected. This is true not 

 only for the albino rat kept in captivity but for the Norway rat 

 when freshly trapped. Although an elimination of the patholog- 

 ical records was difficult on account of the great frequency of 



