2 PROCEEDINGS OF THE ACADEMY OP [Biolog. 



In connection with the first named specimen, Dr. M. referred at some length 

 to the importance of the study of blood crystals in connection with the medico- 

 legal study of the blood, and the examination of blood stains. Dr. M. remarked 

 upon the difficulty of discriminating between the blood of man and that of 

 some other mammals, even when the blood was comparatively fresh and fluid. 

 Here, he thought, the blood crystal might serve to determine the point in 

 question. 



Usually in murder cases, only the dried blood was to be obtained, and here 

 the possibility of making use of the varied forms of blood crj r stals to determine 

 the source of the blood, was a more doubtful matter. Several questions pre- 

 sent themselves. 



Can blood crystals be obtained from the dried blood of man and animals? 

 Dr. M. has so far been unsuccessful in obtaining the characteristic form from 

 dried human blood. Some of the German observers have been more fortunate. 

 The failure to obtain the human blood crystal is not, or would not be, 

 decisive as to the inutility of this mode of research, if the blood of other 

 animals does not present a like difficulty. On this point, our information is 

 not altogether complete, because the number of animals whose blood has been 

 examined, is as yet rather limited. The blood of birds, whether in its wet 

 state, or dried, has not afforded crystals under any method as yet employed. 

 This is unfortunate as regards judicial questions, because it is often a question 

 whether a blood stain may not have been derived from pigeon or chicken 

 blood. Dr. M. referred to such a case as within his own experience. 



The blood of fishes in general affords crystals with great readiness, even after 

 the blood has been long dried. The forms are characteristic, and are not 

 likely to be confounded with those of human blood. 



The blood of all reptiles is difficult to crystallize. Dr. M. would say, after 

 many trials, impossible, were it not for the results which others have observed. 

 At all events no observer has obtained crystals by treating the dried blood of 

 reptiles, nor is it likely that the blood of this class will ever- play any part in a 

 judicial investigation. In regard to birds, fishes and reptiles, it is to be observed 

 that the form of the blood globule, and its nuclear condition, may be decisive 

 as to its not being human, and that the production of blood crystals from the 

 blood of these classes is not, therefore, so important as in the case of mammalia, 

 and especially of the domestic animals. In some of these, as the cat, the blood 

 affords good crystals when properly treated, either in afresh state, or still better 

 when decomposing. Dr. Mitchell was unable to obtain crystals by treating the 

 dried blood of the bullock or sheep, but he obtained crystals easily from the 

 dried blood of the opossum, and from several of the rodentia. It is probable 

 that we shall be able at some future time to obtain crystals from the dried 

 blood of any animal. 



Dr. M. especially insisted on the greater ease with which putrescent blood 

 yielded crystals. He thought that exposure to light and the decomposition of 

 the blood, previous to its being dried, were the most favorable conditions. The 

 disappearance of the fibrinous mass under these circumstances, placed the 

 process of crystallization in the best circumstances by setting free the mass of 

 blood globules. Dr. Mitchell was accustomed to obtain crystals from dried 

 blood by moistening the dried clot and occasionally supplying water until 

 pii' refaction began, when the blood was treated as though it was fresh. 



The blood thus moistened was examined for crystals by the usual method 

 from day to day, but the best results were commonly observed at the period of 

 decomposition. 



Dr. Mitchell's remarks gave rise to an animated discussion of the medico- 

 legal examination of blood stains. 



Dr. Woodward was of opinion, that it generally is impossible to state the 

 particular mammal from 'which the blood of a dried blood stain has come, by 

 any mode of microscopic inspection. Dr. Schmidt had constructed tables of 



[Feb. 



