SYMPTOMS 



The appearance of symptoms of poisoning in sheep by Asclepias 

 Mexicana occurred about five to seven hours after artificial or natural 

 feeding of the leaves or whole plant. 



Five ounces of the dried plant appeared to be the minimum quantity 

 producing symptoms of poisoning in sheep. Three pounds of the dried 

 leaves appeared to be the minimum quantity producing toxic symptoms 

 in a 250-pound calf, with subsequent recovery. 



The first noticeable symptoms in either cattle or sheep are general 

 depression, refusal to eat, and unsteady wobbly gait. The unsteady 

 gait is due to partial paralysis of the hind limbs. Occasionally the 

 paralysis is confined to only one limb. This causes an incoordination 

 in movement, and the animal sways from side to side. Marked muscu- 

 lar trembling is sometimes observed, and in a few hours the animal lies 

 down, refusing to arise. During the period of recumbency tetanic 

 spasms (rigid extension) of the limbs occur at intervals of two or three 

 minutes. 



There is no perceptible elevation of temperature. The pulse rate 

 increases with the duration of the attack and shortly before death 

 may attain the rate of 180 per minute, becoming very thready. Breath- 

 ing is labored and rapid. The head is extended backward and quite 

 rigid. The attack may persist for twenty-four hours, and immediately 

 before death the animal lies in a semicomatose state. In case affected 

 animals recover, the gait is unsteady for two or three days. In some 

 cases incoordinate movements of the hind limbs persist as long as one 

 week after the other symptoms have disappeared. 



POST-MORTEM LESIONS 



These are not especially characteristic. . 



Summarizing the observations of post-mortem lesions in sheep and 

 cattle, the following pathological changes were fairly constant in deaths 

 due to ingestion of Asclepias Mexicana : 



The liver exhibited passive congestion and low-grade cloudy swelling. 

 Kidneys light in color with low-grade cloudy swelling. The mucosa of 

 the abomasum may exhibit congestion of a moderate degree which may 

 be continuous throughout the small intestine. Occasionally marked 

 arborization of the blood-vessels of small intestines is observed. 



Occasional subepicardial petechial hemorrhages are observed along 

 the coronary vessels and auriculo-ventricular border. The heart muscle 

 is pale and friable. 



The pia mater in cerebral and cerebellar regions exhibited a marked 

 congestion on cut surfaces; minute capillary hemorrhages were 

 observed in the medullary portion of the cerebrum and cerebellum, also 

 in the cropus striatum. The lateral ventricles contained a moderate 

 amount of sero-sanguinous fluid. 



Histopathological examination of selected tissues confirmed the 

 observations made at the autopsy. In the brain the hemorrhages were 

 largely from the minute capillary vessels. Occasional interstitial capil- 

 lary hemorrhages were observed in the reticular- tissue between the 

 convolutions of the cerebrum. 



