28 DEPARTMENT OF AGRICULTURE. 



LATENT FORM. 



It is nocessary tliat I sliould draw s])ecial attention to tlie large nnm- 

 bar of cases wliieli run an iiisidions eonrse and pass unobserved. These 

 are the most dangerous, as less care is paid to their isolation. 



APPEARANCES AFTER DEATH. . 



Animals that are slaughtered, or are permitted to die in advanced 

 stages of the lung plague, ])resent tlie following characteristics: 



The internal changes are contined almost entirely to the chest. On 

 opening this, by splitting the brisket, as the animal lies on its back, 

 layers of yellowish, friable, false membrane, of varying tenacity, stretch 

 across around the sac (pericardium) containing the heart. These adhe- 

 sions exist on one or both sides of the chest, and are sometimes alto- 

 gether absent. They are found bathed in a yellowish, grumous fluid or 

 serum, highly charged with albumen and shreds of solid deposit. Por- 

 tions of one or both lungs are found more or less tirndy adhering to the 

 membrane (pleura) covering the ribs and diaphragm, and in i)assingthe 

 hands, especially round the large posterior lobes of either lung, it is 

 ditlicnlt, in advanced stages of the disorder, to detach the diseased por- 

 tions of the organ from the ribs. 



The false membranes, disposed in laj^ers which may be stripped oft" 

 the pulmonary surtace, are found adhering more or less closely to it, and 

 the membrane (pleura) covering the lung, which is usually smooth and 

 glistening, is rough, of a njottled color, and with more or less marked 

 papillary or warty-looking eminences. These are the vascular oft'shoots 

 of the membrane feeding the deposit around, and in time the process of 

 growth and formation of vascular or blood-carrying tissue may lead to 

 as solid a connection between the lung and the sides of the chest as 

 between healthy tissues. Such complete development is only seen iu 

 very chronic cases, or animals that have recovered from the disease. 



The fluid around one or both lungs varies in amount from a few ounces 

 to several gallons. At times it is tolerably clear when warm, and gelatin- 

 izes on cooling. At others it is diflicnlt to separate it from the shreds 

 of lymph and false membranes in the meshes of which it is held. Pus 

 cells frequently abound in it, and it assumes in a few cases the character 

 of pus. It is especially purulent when abeesses have formed in the gan- 

 grenous lung tissue, and an opening has led to communication between 

 the lung tissue and the pleural sac. Under these circumstances, the 

 fetor noticed on opening the chest is intolerable. 



On removing the lungs, great variations in extent, but uniformity in 

 essential appearances, of disease exist. 



In recent and mihl cases, one lung is found aff'ected. Its surface may 

 be smooth from the absence of deposit around it. Parts of the organ 

 are collapsed, as iii health, and the usual normal i>ink color is noticed. 

 The allected pai't is swollen, hard, and mottled. On cutting into this, 



