LARKSPUR POISONING OF LIVE STOCK. 75 



Although Delphinium harbeyi was common in the pasture, no trouble 

 had been experienced from this source, probably because there was 

 an abundance of good feed. Moreover, none of the experimentally 

 fed animals had been poisoned since August 8, on account of the 

 diminished toxicity of the plants. The autopsy showed that No. 633 

 had died of asphyxia, as it had vomited, and the stomach contents 

 were found in the larynx and trachea. As the animal had been dead 

 for two or three days, the autopsy was unsatisfactory, but, so far 

 as it could be made, showed conditions typical of larkspur poisoning. 

 A careful examination of the contents of the rumen demonstrated 

 the presence of a large amount of stems and seeds of Delj)hinmm 

 harbeyi. This, then, was clearly a case of larkspur poisoning- in 

 which the seeds were the most important factor, for it was too late 

 in the season for the leaves to produce poisoning. 



AGE OF PLANTS AS AFFECTING TOXICITY. 



From a careful examination of the charts for the feeding of 

 Delphinium harheyi and Delphinium menziesii certain facts are 

 brought out quite clearly in regard to seasonal changes in toxicity. 

 If an average curve were made for the charts of Delphinium harbeyi 

 feeding in 1909, 1910, and 1911 (figs. 6, 7, 8, 10, and 11), it would be 

 found that the quantity necessary to produce poisoning increases pro- 

 gressively from the first of the season until the time when seeds are 

 formed in the plants.. Taking into account the length of time 

 during which the plant was given in individual cases, the appar- 

 ently aberrant cases of very large quantities in these years are easily 

 explained, as, in those cases, by reason of the prolonged feeding, 

 there was more or less elimination of the poison. 



It is a striking fact that the smallest quantity needed to produce 

 poisoning was in the earliest cases. It seems quite clear that Del- 

 phinium harbeyi progressively loses toxicity after blossoming until 

 the time when the seeds are formed. At this time the leaves and 

 stems are not particularly toxic and if the seeds were disregarded, 

 the curve would indicate diminished toxicity from early in the 

 season until the middle or last of August, at which time on the Colo- 

 rado ranges the plant becomes perfectly harmless. 



As a matter of fact, stock on the range do not eat the seeds of 

 Delphinium barbeyi to any extent, so that the fact that the seeds are 

 especially toxic has little practical bearing so far as the stockmen are 

 concerned. It may be stated as a general fact that after the middle 

 or latter part of August, depending upon the season. Delphinium 

 harbeyi ceases to be poisonous, and under ordinary range conditions 

 in Colorado few cases of poisoning occur after the middle of July. 

 Not only does it cease to be injurious, but it has been noticed that 



