[167] The name "cytases" or "alexins" has been given to hemolyzing diastatic substances which are found in certain serums. It has been known for a long time that the serum of the blood of many animals destroys the red blood-corpuscles of other and different species. The chemical composition of these cytases or alexins is not yet definitely known, but the substances rank among the albuminoids; they are destroyed by a temperature of 55° to 56° C., and act only in saline solutions (Ehrlich and Morgenroth, _Berlin. Klin. Woch._, pp. 6 and 481). The cytases or alexins, which will be studied in another volume of this collection, and which will discuss the active principles of the immunizing serums, constitute one of the numerous soluble intraleucocytary ferments, and they pass into the serous liquids of the organism only as the result of a rupture of or injury to the phagocytes. As to the blood of the hedgehog, we have already seen that Physalix and Bertrand have shown that it may be a counter-poison towards serpent-venom under certain conditions. In its normal condition it is highly toxic. =Poisonous Meats.=--It is particularly among the fish that we find these normally present, and it is a singular fact that, for a given species, the toxicity frequently depends upon the period of the year. Thus, at the period of spawning, certain fish may be extremely poisonous, or, on the contrary, may entirely cease to be so. The anchovy ballassa from the shores of India occasions death even in very small quantity; the poisonous meltite of the same seas causes violent vomiting; the fugu of the Japanese seas possesses an extreme poisonousness at the spawning period, while, on the contrary, it is perfectly innocuous at all other periods. Numerous cases of poisoning have been chronicled every year by the journals, due to the ingestion of mussels; in the flesh of these crustaceæ is found a dangerous toxin, _methylotoxin_. The flesh of oysters is also unwholesome at the spawning period. The toxic symptoms caused by these animals become apparent in not less than twenty-four hours after ingestion. The poisoning due to these fresh meats must not, however, be confounded with that caused by tainted or spoiled meats. WORKS OF ALFRED I. COHN PUBLISHED BY JOHN WILEY & SONS. =Indicators and Test-papers.= Their Source, Preparation, Application, and Tests for Sensitiveness. With Tabular Summary of the Application of Indicators. Second Edition, Revised and Enlarged. 12mo, ix + 267 pages. Cloth, $2.00. =Tests and Reagents.= Chemical and Microscopical, known by their Authors' Names; together with an Index of Subjects. 8vo, iii + 383 pages. Cloth, $3.00. _TRANSLATIONS._ =Fresenius's Quantitative Chemical Analysis.=