Diphiheritie Membrane and the Croupous Cast. 81 



or wliite-of-egg-like, and of a pale yellow colour ; easily separable 

 from the subjacent surface, as an imperfect cast of the part on 

 which it is formed. It is only as a post-mortem deposit, or when 

 it has been steeped in a weak ammoniacal solution of carmine, 

 that it is seen otherwise than a viscid secretion, or a single layer of 

 cells. It is generally thrown off in a membranous form, or rather 

 separated during a tit of coughing, when the patient finds almost 

 immediate relief from the more urgent symptoms of the attack. It 

 is never so intimately connected with the subjacent mucous mem- 

 brane as to cause bleeding if detached by force, although there may 

 be some tumefaction about the parts. In short, it is a simple 

 epithelial layer or cast of the superficial structure, closely re- 

 sembling the skin shed by some of the lower animals — the growing 

 amphilia, for example — an outgrowth of epithelium cells under- 

 going degeneration of protoplasm, and entangling granular mole- 

 cules. Such a cast is, however, thrown off with difficulty by a 

 feeble delicate child. 



The histological characteristics of the felt-like membrane of 

 diphtheria are even more strongly marked than those just enume- 

 rated. A small portion of a fresh exudation requires a good deal 

 of careful teazing out to fit it for microscopical examination under 

 a power of 350 x . The normal tissues are seen to be replaced by 

 an aggregation of compressed cells, molecules of fat, connective and 

 fibrous tissue, a few crystals, muco-purulent or glandular corpuscles, 

 foreign bodies, as starch granules or other portions of food, and 

 spores of the Oidium albicans. It is surmised, therefore, that the 

 dense felt-like membrane is made up of superficial and deep tissues ; 

 mucous membrane, voluntary and involuntary muscles and glands, 

 and produces great tension and decomposition or ulcerative 

 destruction. Even the cartilages are at times involved, and the 

 cells become fusiform. That the mucous membrane itself is 

 affected by the infiltration as well as the more superficial struc- 

 tures is quite evident by the loss of sensibility in nerve fibres.* 



The drawing. Fig. 1, made from a dried preparation, exhibits 

 most of the changes spoken of. For showing the structures 

 involved in the morbid state produced by the disease, it is better, 

 after careful removal of the membrane, to immerse it for a short 

 time in a staining fluid, and then dry it. Fine sections cut from 

 such specimens must be mounted in dammar or balsam. 



In preparations made from other cases of diphtheria I noticed 

 considerable tumefaction, which appeared to compress the vessels 

 and arrest circulation and nutrition ; not a trace of columnar 

 epithelium will be seen in any specimen. Those who have failed 

 to find evidences of connective and fibrous tissue in the diphtheritic 



* Virchow is also of opinion that an exudation takes place into the substance 

 of the mucous membrane, and produces tension and subsequently ulceration. 



