from fifteen minutes to an hour a chill occurs, followed by high fever, a temperature of 103° to 105°, and the patient may become delirious. Jaundice may appear later. The macroscopic appearance of hæmoglobinuria is almost constant.” (Peterson.) In a fatal case recorded by other writers the chief symptom was hæmoglobinuria, which progressively increased until the functions of the kidney became so much interfered with by deposits of hæmoglobin or damaged corpuscles that the patient died with suppression of urine and all the signs of uræmia (25). In other cases a slighter and transient hæmoglobinuria has been noticed, showing that some destruction of red cells has taken place without producing any further effects. This symptom is, of course, due to hæmolysis following reactions between the serum and corpuscles as explained above. The variation in degree of the reaction is to be partly explained by the fact that there are three possibilities: (1) The donor’s corpuscles may be hæmolysed by the recipient’s serum; this will result in the transient hæmoglobinuria and wastage of the transfused blood; (2) the recipient’s corpuscles may be hæmolysed by the donor’s serum, or (3) serum of each may hæmolyse the other’s corpuscles. Either of the latter events will be extremely serious. As already mentioned, hæmolysis is always preceded by agglutination, and it seems that the agglutination may be the more rapidly fatal of the two. It was probably this that was chiefly responsible for the suppression of urine in the case referred to, and a case has been recorded in which it appeared to be the only cause of immediate death or, as an American writer expresses it, “sudden exitus took out, out of a clear sky,” owing to the presence of multiple emboli. In addition to the evidence of hæmolysis the patient may exhibit the symptoms described above. Sometimes the urticarial rash has been accompanied by vomiting and headache. This group of symptoms suggests that the condition is analogous to the anaphylactic shock which may follow the intravenous injection of any foreign protein. The symptoms in a mild degree do occasionally follow the transfusion of blood which has been shown to belong to a compatible group, and it had been found to develop even to an alarming extent after the later transfusions, when a series was being given for a condition such as pernicious anæmia (34). In such cases, however, as is suggested elsewhere, this may, perhaps, be regarded as true anaphylactic shock. The symptoms which may accompany a first transfusion cannot be identical with this since true anaphylaxis must have been preceded by sensitization with a minimal dose of foreign protein introduced into the circulation.