SECRETARY'S REPORT. 17 



not of an inflammatory nature at its outse^, and that inflammation is 

 rather tlie resiilt than a cause of the disease. It is difficult to exj)lain 

 the precise change which takes phice in the blood from the opei-ations 

 of the aerial poison; but it appears to me that the vitality of the ii1)rine 

 is interfered with, and that it, with the albuminous constituents of the 

 fluid, also altered in quantity, is transuded from the capillary vessels, 

 and finds its way into the areolar tissue of the lungs, accunudating 

 where this tissue exists in greater abundance, namely, in the interlobular 

 spaces. This inordinate transiidation seems to depend on a tendency in 

 the blood to separate into its several constituents, arising most likely 

 from the diminished vital force of the fibrine, and an arrestation to 

 the conversion of the albumen of the serum into fibrine. The fibrino- 

 albuminous portions of the fluid are thus changed, and probably aug- 

 mented, and their exudation is a natural consequence of such condition. 

 The red corpuscules being in part deprived of the liquor sanguinis in 

 which they float, are retained in the capillaries, where they accumulate 

 in unlimited numbers, obliterate their passage, and compress the air- 

 cells they surround, so as to stay the entrance of the air, and produce, 

 as elsewhere stated, the dark-colored spots which stud the lungs. It is 

 these eifusions, and the obliterated condition of the vessels, which give 

 bulk, increased weight and solidity to the lungs, and destroy their 

 functions as aerifying organs. From this explanation it is evident that 

 I regard pleuro-pneumonia to approach nearer to a dropsical than to an 

 inflammatory disease." 



PERIOD OP INCUBATION. 



From the foregoing it appears that from forty-two to sixty days is the 

 time of incubation with animals such as have been used to experiment 

 ynth the past year ; in the one well advanced in pregnancy, (No. 2, 

 Weston,) a longer time elapsed, fifty-six to seventy-one days, before 

 Avell marked symptoms appeared, though the slight cough and the firm 

 adhesion to the mediastinum indicated that the animal Avas affected at 

 the earlier period above named. 



If it is desirable to experiment further in relation to the contagiousness 

 of the disease, and the effect of the disease upon the milking, fattening 

 and breeding qualities of the animal affected, it appears to me that an 

 experiment upon a much larger scale should be made. I Some months 

 ago submitted a verbal proposition like the following : 



That a herd of twenty well-fed animals, the cows good milkers, be 

 selected, and either remain where they have been kept, or removed to a 

 good barn, and tied up as animals are usually kept fastened. That 

 when an animal of another herd is unmistakably affected with the 

 disease, and has exposed freely for four days, say three on each side, 

 3* 



