498 DISEASES OF THE SKIN. 



phor. When the acne nodules appear, the preparations of sulphur may 

 be employed ; but, instead of the paste recommended for the cure of 

 acne vulgaris and sycosis, it is better to use IZummerf eld's lotion, or a 

 turbid mixture of sulphur and water, or alcohol. In old cases, almost 

 every treatment will prove ineffectual. 



V. HAEMORRHAGES OF THE SKINPURPURA. 



ETIOLOGY. All haemorrhages of the skin proceed from a solution 

 of continuity of the walls of the cutaneous vessels ; blood never trana 

 udes through the wall of a blood-vessel, unless it be ruptured. Pur- 

 pura are reddish, bluish, or blackish spots, the result of extravasation 

 of blood into the parenchyma of the cutis, the blood filling up the in- 

 terstices between the elements of the cutaneous tissues, but causing 

 no swelling of the skin. When the purpura are small and round, they 

 are generally called petechice / when elongated into stripes, they receive 

 the name of vibices; and when diffuse and of irregular shape, they are 

 called ecchymomata. If the effusion of a somewhat large quantity of 

 blood causes the skin to swell in the form of small nodules, we have 

 the lichen lividus ( Willan), or the purpura papulosa (Hebra). The 

 broader flat tumefaction of the skin caused by a more diffuse extrava- 

 sation, and which resembles the wheals of nettle-rash, is called pur- 

 pura urticans. Sometimes a haemorrhage separates the epidermis 

 from the papillary layer, forming blebs, purpura bullosa ; hi other 

 cases the blood perforates the epidermis and appears upon its exterior. 

 In the so-called " bloody sweat," blood really exudes through the pores 

 of the skin. It is not mingled with sweat, however ; and since, more- 

 over, this bleeding has nothing to do with the secretion of sweat, the 

 above term is inappropriate. 



The causes of haemorrhage into the skin are : 



1. External injury. The traumatic haemorrhages caused by the 

 bites of fleas deserve some attention, since inexperienced physicians 

 are occasionally misled by them, and are induced to diagnosticate 

 some serious disease of the blood. Immediately after the bite of a 

 flea, a roseola spot or wheal makes its appearance, in the middle of 

 which the small, dark-red wound the stigma is perceptible. 



Besides this, however, in persons whose blood is deficient in fibrin, 

 a haemorrhage takes place into the cutaneous substance, about the 

 puncture, similar to that much more considerable extravasation which 

 occurs around a leech-bite in persons of a similar constitution. These 

 little haemorrhages from flea-bites continue visible after the puncture 

 has disappeared ; so that, although the stigma may afford a distinctive 



