ZOOLOGY. 389 



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criminating 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 pos- 

 sibility of making use of the varied forms of blood-crystals to determine the 

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

 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 fortu- 

 nate. 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 ani- 

 mals 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 ques- 

 tion 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 espe- 

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

 affords good crystals when properly treated, either in a fresh state, or still 

 better, when decomposing. Dr. M. 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 prob- 

 able 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. M. was accustomed to obtain crystals from 

 dried blood by moistening the dried clot and occasionally supplying water 

 until putrefaction 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 mcdico- 

 k';v.l 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, 



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