ROSACEAE PRUNUS 517 



substance from which prussic acid is obtained. Mr. Chesnut says in regard to 

 the black cherry : 



The fruit is rather agreeable, being but slightly bitter and astringent in taste. In 

 some localities it is much used to flavor liquor. Poisoning is frequently caused by cattle 

 eating the wilted leaves from branches thrown carelessly within their reach or ignorantly 

 offered as food. Children occasionally die from eating the kernels of the seed or from 

 swallowing the fruit whole. 



Prof. Chas. D. Howard, of the New Hampshire Station, says: 



The poisonous property of all species of cherry leaves is due to hydrocyanic acid, 

 popularly known as prussic acid. This compound does not exist as such in the growing 

 leaf, but is derived from a class of substances called glucosides, of which amygdalin is the 

 type peculiar to the cherry. This, or a closely allied body, is to be found not only in the 

 leaves and bark, but especially in the stones of cherries, peaches and plums, and the seeds 

 of the apple. By the action of moisture and a vegetable ferment called emulsin, which 

 exists in the plant, a complex chemical reaction takes place, that begins in the leaf the 

 moment connection with the circulatory system is cut off. The three products of this re- 

 action are hydrocyanic acid, grape sugar and benzaldehyde, or bitter almond oil. 



There is a popular opinion that the leaves of the cherry are poisonous only when cut 

 and in the wilted condition; that cattle may safely nibble them from the growing shrub 

 without danger of injury; and that they are quite harmless when dried. Our observations, 

 however, prove these views to be but partially correct. As a matter of fact, distillations 

 of samples, made within twenty minutes of cutting, show that the freshly cut leaves yield 

 nearly as much acid as the wilted ones do when calculated on the weight of fresh material 

 taken, and when eaten fresh, the character of the juices within the animal stomach is such 

 as to render that organ a most favorable place for the conduct of the reaction in which 

 prussic acid is liberated. 



On the other hand, while it is true that the thoroughly dried leaves yield a comparatively 

 small amount of acid, still they may always produce some, and as ordinarily dried in the 

 hayfield, they may be capable of generating a considerable quantity of the poison. The 

 desirability of carefully excluding them from all hay is therefore apparent. 



One hundred grams of bitter almonds (.Prunus amygdalus communis), in the form of 

 pulp, yield 250 milligrams prussic acid; the same amount of kernels from cherry stones 

 yields 170 mgs.; leaves of the cherry laurel (Prunus Laurocerasus), occurring in Europe 

 and Mexico, 39 mgs.; kernels of peach, 164 mgs.; apple) seeds, 35 mgs. The stones of all 

 these species must therefore be regarded as dangerous; the fruit, in every case, so far as 

 can be ascertained, is harmless. 



The leaves of the wild black cherry are the most poisonous of the three species in- 

 vestigated, though all are dangerous. 



Both the wilted leaves and fresh leaves are poisonous, while the dried are to be re- 

 garded with suspicion. 



Vigorous, succulent leaves from young shoots, which are the ones most liable to be 

 eaten by cattle, are far more poisonous than the leaves from a mature tree or stunted 

 shrub. 



Leaves wilted in bright sunlight to about 75 per cent original weight, or until they 

 begin to appear slightly limp and to lose their gloss, yield the maximum amount of prussic 

 acid. 



I have seen cattle browse on the leaves of Prunus demissa in the Rocky 

 Mountains. It is believed by stockmen to be poisonous. Probably the danger 

 is not so great because the leaves are eaten direct from the tree ^nd not wilted. 

 The Bureau of Forestry has shown that much loss occurs which can easily be 

 prevented by changing the trail. 



It has been known for a long time that seeds of the various members of 

 the genus Prunus contain poisonous properties. The bark of several of our 

 wild cherries is also known to contain a poisonous principle, a ferment known 

 as emulsin, which in the presence of water acts on the glucoside amygdalin 

 C 2Q H 27 NO 11 , and produces hydrocyanic acid, a powerful poison; it is a clear, 

 colorless liquid of a characteristic taste and odor, resembling that of a bitter 



