BOVINE DIPHTHERIA. 
463 
characterized by the coagulation, not merely of the epithelium, 
but also of the underlying connective tissues. 
The affected patch is swollen and assumes a whitish or greyish 
tint, the discoloration extending through the epithelium to the 
connective tissue structures. The epithelium in some cases is 
lost altogether, and then the diphtheritic patch consists of dead 
connective tissue only. The patch is turbid and granular in 
texture, or it may be homogeneous or composed of amorphous 
hyaline blocks. The nuclei are always more or less completely 
lost. The small vessels which permeate the patch show signs 
of a homogeneous transformation of their walls. 
The necrotic tissue is separated from the living by a zone of 
cellular infiltration. Fibrinous filaments are seen here and there 
through the mass. The lymphatics in the neighborhood con¬ 
tain coagula and leucocytes. Necrotic process may attack any of 
the mucous membranes ; it is especially common as a result of 
infection of one kind or another. It is often demonstrated that 
it is associated with the invasion of the tissue by bacteria. 
The formation of the necrotic patch or slough is, of course, 
not the first stage of the diphtheritic process. The sloughs 
themselves act as irritants and set up inflammation around them. 
Superficial epithelial sloughs become in this way infiltrated with 
pus and so are loosened and cast off. The loss of substance is 
then made good by regenerative multiplication of the remaining 
epithelial cells. Larger and deeper sloughs may in like manner 
be separated by suppurative inflammation taking place around 
them, and the deficiency is then made up by the formation of a 
cicatrix, which in process of time may be covered over with a 
new epithelium. 
But the process often maintains its destructive character for 
a considerable time, extending continually to greater depths, and 
often inducing intense purulent inflammation over a wide area 
around the initial lesion. 
Sometimes the necrotic inflammation takes on a gangrenous 
character, that is to say, micro-organisms penetrate the diseased 
tissues and set up in them septic or putrid decomposition. The 
