98 PATHOLOGY. 



more especially those of horned cattle and sheep, are caused by 

 an altered condition of the blood. How this determines a con- 

 gestion of an organ or a system of organs it is difficult to under- 

 stand ; but such diseases as apoplexy of the spleen, quarter-ill, 

 and other anthracoid diseases manifested by extensive congestions 

 and extravasations, are all due primarily to blood alterations, 

 the lesions of organs being secondary to and depending upon 

 the blood disease. A thin watery state of the blood, as well as 

 the presence of some specific blood poisons, and the operation 

 of malarious influences, have also in many cases a tendency to 

 cause congestions of organs. 



4. Defective secretion, either from an organ or a secretory sur- 

 face, is a cause of congestion of such an organ or surface ; and it 

 is found that the means which increase the secretion will often 

 remove the congestion. It must, however, be borne in mind 

 that diminished secretion is usually the result of the congestion, 

 and that the means which have the power of exciting the secre- 

 tion of such a part very often, in virtue of their irritating effects 

 up)on it, increase the congestion, or, what is perhaps of greatei 

 moment, transform a mere congested condition into that of in- 

 flammation. 



Many writers seem to confound congestion with inflammation, 

 and we continually see slight inflammations described as con- 

 gestions. It appears to me that a distinction should be made 

 between the two conditions, and tliat a congestion should be 

 defined to be a fulness of the vessels of a part or parts arising from 

 various causes, without the occurrence of any primary important 

 perversion of the nutrition of that part ; and that inflammation 

 is a perverted condition of the nutritive function of a part, 

 accompanied in the majority of cases by a congested condition 

 of its vessels ; such congestion, however, not being necessary to 

 the inflammatory process, for it is found that inflammation 

 involves the non-vascular as well as the vascular structures of 

 the animal body. 



The results of mechanical congestion are transudation of 

 serum, haemorrhage, thrombosis, and gangrene ; and of active 

 hyperaemia, increased redness, elevation of temperature, and a 

 sense of throbbing, succeeded, if the congestion continues, by 

 enlargement of the small arteries and thickening of their walls ; 

 function being in some cases exalted, more especially if the 



