PUEPUEA. 517 



of soda checks, to a marked degree, putrefactive changes in the 

 blood ; and, also, during constipation, neutralizes the foul gas 

 given oft* by the residue of the food which is in the intestines. 



llobertson describes a dangerous form of diabetes insipidus, in 

 which the urine is dark coloured, thick, and of high specific 

 gravity, owing to the presence of a peculiar form of albumin. 

 There is rapid wasting, followed by paralysis and coma. 



Excessive urination after diseases of the organs of breathing, 

 should not be interfered with ; for it is an effort of nature to get 

 rid of the effete matter which is taken up by the blood, on the 

 products of the previous inflammation becoming broken up. The 

 waste matter with which the blood is loaded, irritates the kidneys 

 and gives rise to the profuse staling. 



Purpura Haemorrhagica {Petechial Fever) 



appears to be a grave alteration of the blood due to the intro- 

 duction into the system of virulent material produced under bad 

 sanitary conditions, or generated within the body during previous 

 illness; or it may be caused by constitutional taint or weakness. 

 As a rule, it follows some debilitating disease, such as strangles, 

 influenza, or catarrh ; in which cases, it appears during the stage 

 of convalescence. It is not infectious, it cannot be communicated 

 by inoculation, and no characteristic microbe has been found in 

 horses suffering from it. Up to the present, nothing is known 

 about its cause. It somewhat resembles the purpura haemorrhagica 

 of man. 



NATURE OF THE DISEASE.— We may roughly say that the blood in 

 purpura, is in a more or less decomposed state. The amount of albumin in 

 it is greatly diminished ; the red corpuscles are more or less shrivelled and 

 broken up ; and the watery constituents show a marked tendency to separate 

 themselves, and, consequently, rapidly ooze through the walls of the blood- 

 vessels ; thus producing the characteristic swellings. The infiltration of this 

 fluid into the brain, in excessive quantity, causes insensibility ; and into the 

 lungs, suffocation. The fluid which thus escapes, holds in solution a quantity 

 of the colouring matter of the blood, which is obtained from the broken-up red 

 corpuscles, and which causes the various infiltrated tissues to become stained : 

 hence, the name purpura htemoiThagica. The blood itself is darker than 

 usual, owing to changes undergone by its colouring matter. It also lofes, to 

 a marked extent, its property of coagulating. 



Whether the blood only is affected, or whether the walls of the vessels are 

 also implicated, are questions which our present state of knowledge does not 

 enable us to answer with certainty. 



VARIETIES OF PURPURA.— For practical purposes, we may 

 regard this disease as appearing under two forms, namely, severe 

 and mild. 



SYMPTOMS OF SEVERE PURPURA.— The most noticeable 



