It will be remembered that in speaking of the bile-acids, I mentioned that while glycocholic acid is a crystalline, taurocholic is a non-crystalline substance. Tyrosine, and leucine stand in a similar relation to each other; tyrosine being crystallizable, leucine non-crystallizable. Now, taking this fact into account, together with the fact, that when the bile-acids are allowed slowly to enter the circulation, they reappear in the urine, accompanied with tyrosine, and leucine; and also with the third fact of these latter substances being found in the liver when the biliary function is interfered with, I am inclined to look upon tyrosine, and leucine as the products either of the arrested, or of the retrograde metamorphosis of glycocholic, and taurocholic acids. Moreover, I have found in one case, after injecting bile in the way before mentioned, into the cellular tissue, crystals of tyrosine spontaneously form in the bile taken from the animal's gall-bladder after death, and merely allowed slowly to evaporate. This result strengthens the foregoing opinion. Frerichs states that he has never detected the biliary acids in the blood, even after bile had {98} been injected into the circulation. In a remarkable case where 1 oz. of ox-bile killed a dog in less than five minutes from the time it began to be slowly injected into the jugular vein, I detected the bile-acids in a clear extract of the blood, with facility. This leads me to mention that, contrary to the statement of Frerichs, and in accordance with that of Kühne, the injection of the pure bile-acids into the blood is very dangerous, and that even the injection of pure bile into the cellular tissue, often proves fatal in the course of twenty-four hours, thereby showing that the constituents of the bile are highly poisonous. In illustration of these facts I may cite the following experiments:--