THE DISEASES OF CATTLE. 131 



Dr. Mclihenny thus sums up the reasons which lead him to consider the tremblet 

 as the etiect of the Rhus Toxicodendron, or poison oak. 



" To sum up our conclusions on the cause of milk-sickness, we must be allowed to 

 express our decided conviction, that it is produced by the Rhus Toxicodendron, or 

 Poison Oak, for the folluwing reasons : — 



I. Sick stomach does not prevail where there is no rhus— that in every section of 

 country where none of the small rhus can be found, there can be none of the trembles 

 found. 



•2. It does universally exist where there is an abundance of the smaller rhus, 



3. It never occurs until vegetation comes furth in the spring. 



4. Where it prevails most,~the rhus is in its greatest luxuriance. 



5. After the heavy frosts kill all vegetation, the disease subsides. 



6. It is a well-kiiowu fact, that cultivation kills the Poison Oak — entirely de- 

 Btrovs it. 



7. It is equally as well established, that animals kept within a well-cultivated 

 enclosure, are perfectly exempt from the disease. 



8. Almost every observant and inteliigenl individual who has been raised amidst 

 the disease, has come to the conclusion, that the Rhus Toxicodendron is the cause of 

 milk sickness. 



9. That it is distinguished from the Radicans, or common Poison Vine, by its dif- 

 ferent number of leaves— also, by its acriduess of character. 



10. A certain locality produces the disease, find it where yoj may, such as flat, 

 heavy timher-land, interspersed with hazle and other underL.ush, which is quite 

 productive of the rhus. 



II. 'I'he seldom appearance of the disease on hilly, dry gfrounr", is in consequence 

 of such a place not being congenial to the production of that plunt, so that what 

 little does exist, is not so apt to produce the disease, in consequence of its unhealthy 

 growth." 



The PATHOLOGY of the disease is thus described by the same author :— 



" As to the pathology of this disease I know but little. I have treated quite a 

 number of cases, but have never been favoured with a post mortem examination; 

 consequently, I have had no other means of ascertaining morbid appearances than 

 that of judging from symptoms : the mere external developments of the internal con- 

 dition. We are told, "however, that in animals which die of this disease, the mavy 

 folds, or mesentery, is in a hard, dry condition, and, in many cases, perfectly black ; 

 and that all the folds which lie enclosed in the bowels, and are in close contact with 

 them, are frequently in such a brittle condition, that they can be readily broken, 

 particularly those that envelope the stomach; and that traces of inflammatory ac- 

 tion can be frequently discovered the whole length of the intestinal canal; but the 

 greater amount, those that have left the deepest marks, are to be seen in and around 

 the stomach and duodenum. 



" If this should be a true condition of the morbid appearances of the animal, which 

 we are satisfied it is, we may reasonably expect that the same results are to be seen 

 in the human subject. So far", however, as my opinion goes, I believe that the poison, 

 when taken into the stomach, produces inflammation of that organ, particularly 

 confined to the mucous coat; that inflammation contiuuin?, tliickens the mucoug 

 lining to such an extent, that it closes, in proportion to its severity, the passage 

 from the stomach to the bowels. I am satisfied that there is inflammation down to 

 the upper part of the bowels, but, generally, in a slight degree. I do not believe that 

 there is anv general inflammatory condition of any of the chylopcetic viscera, but 

 that the entire force of the disease is spent upon the stomach, and, perhaps, duo- 

 denum. 



" From what observation I have been able to make upon the subject. T am inclined 

 to the opinion that the lower portions of the bowels remain, measurably, if not en 

 tirely, exempt from inflammation ; that it is entirely a disease of the st<unach ; tha 

 in proportion to the severity with which that organ is attacked, in that proportion 

 will IhechvlopcEtic viscera become deranged. 



" Another proof that the disea.se is inflammatory, is the constipated condition of 

 the bowels. There could not be such a dry and harde^ned condition of the fecal matter 

 produced by any other derangement, excepting that of inflammatory action. 



"I have been led to make these remarks, in consequence of an opinion that is 

 prevalent with some of our practitioners, that the disease is nervous; that the g^jat 

 gastric irritability is, or might be, attributed to nervous excitement. This, to me, 

 appears imp-^ssible ; for, if the nerves of the stomach were in such a morbid condi- 



