RfcPO&T ON DO Oft INK. 57 



tbe skin dependent on nerve disorder. Th,; p:it-h or jiU-juu is a 

 irvumseribed (edema of the skin due to paralytic dilitation of the 

 arterioles, followed by an exudation of serum and ini^ r; iti"n of 

 leucocytes. According to Neisser, the proce-s in the human 

 subject consists in an increased secretion of the lymph in the 

 neighbourhood of the capillaries of the skin, this in turn causes 

 compression of the vessels and explains the bloodless centre of the 

 patch. The variations in characters of the plaque are due to the 

 different depths to which the infiltration penetrates. In the 

 ordinary form of urticaria, only the upper layer of the integument 

 is affected, while in U. gigas or what is called the acute circum- 

 scribed cadema o Quincke, the whole thickness of the skin is in- 

 volved. This form of the disease is characterized by the development 

 of patches of localized oedema of large size. They are hard to the 

 toueh, surface more or less round, itching seldom a symptom, only 

 last a day or two and subside as quickly as they come. When 

 there is much loose connective tissue which offers comparatively 

 little resistance to the diffusion of the infiltration, it is termed 

 U. ccdematosa. The predisposing causes of Urticaria may be 

 divided into topical and systemic, but in this connection we need 

 only consider the latter. It may be noted that " malaria is so 

 strong a predisposing cause, that some writers make a special 

 variety of the affection, under the name of paludal urticaria." 

 Much more, therefore, may we emphasise the eruption of plaques 

 during the course of Dourine, for they are almost pathognomonic 

 of that malady and the chief symptom for arriving at a correct 

 diagnosis. 



V. What is the primary cause of a p laque ? The imprison- 

 ment of the trypanosoma or its developmental forms in the papillary 

 layer of the skin, the production of a toxin by the protozoon. The 

 toxin produces a vaso-neurosis, dilitation of the capillary vessels, and 

 an increased secretion of lymph in the neighbourhood con- 

 fined to a circumscribed area. In blood drawn from a plaque shortly 

 after its eruption, the haematozoon appears to be i>erfectly formed, 

 but is small in size, and the undulating membrane is not so well 

 marked as in the mature protozoon. This physical condition might 

 point to the fact that it had developed from the amoeboid or 



