the privilege of reproducing Dr. C. Meymott Tidy's beautiful plate representing this test. same. Vide Tidy Legal Medicine for No matter how small the quantity of blood, if any red coloring matter remains, in good, careful hands, in the minutest test, the presence can be certainly indicated. Sorby says that a spot of blood of only one-tenth of an inch in diameter, or a quantity of red coloring matter equal to only the 1000th part of a grain was sufficient to give conclusive evidence of the presence of blood by spectral analysis. And the late Dr. Richardson, of Philadelphia, stated that he was able, by a still more delicate process, to detect the 3000th part of a grain of blood, on an axe handle supposed to have been used in a case of murder. THE MICROSCOPE AND ITS POWERS. We have shown how readily mammalian blood can be distinguished from the oval and nucleated corpuscles by this marvelous instrument. We shall conclude what we have to say upon the question as to whether, by the aid of the microscope of high powers, there is any means now known to science of distinguishing between the blood of man and the domestic animals. It was claimed by Taylor, one of the highest authorities, that, in his day, no certain method existed of distinguishing human from other mammalian blood, when it had been once dried on an article of clothing, or upon a weapon, and his editors have, since his death, made the same claim. (Taylor, 12th London Edition, p. 279.) The learned editor of Taylor's Medical Jurisprudence, to whom I refer, Dr. Thomas Stevenson, of London, quotes in the same volume approvingly the valuable labors of Dr. Richardson, of Philadelphia, as reported in American Journal of the Medical Sciences, July, 1874, that by the use of the microscope of higher powers, up to 750 diameters, and by other 139 appliances, he had been able to distinguish, under favorable conditions, the blood of man from such animals as the ox and pig and to give evidence thereon in certain trials for murder. Taylor and other observers before Richardson had Vide figures 3 only used 300 to 800 diameter powers. Red Blood Corpuscles, 315 diamaters. a. Red Blood Corpuscles, 315 diamameters. b. White Corpuscles. The method is to contrast the diameters of the red blood corpuscles of man with each of the mammalian animals. Fig. 5. Fig. 6. Human Corpuscles, 650 diameters. Pig's Corpuscles, 650 diameters. 1-4250, Dr. Seiler's measurements.. The diameter of the red corpuscle of each mammal has been ascertained approximately by averages. The difficulty lies in the exactness of the standard. For example, the average diameter of the human red blood corpuscle is 1-3200ths of an inch. Vide fig. 5. Reese says the maximum is 1-2000, Fig. 7. Red Blood Corpuscles magnified 319 diameters. a. The Dog. c. The Rabbit. Fig. 8. d. The Ass. minimum 1-4000. Dr. Stevenson places the maximum at 1-3000 and the minimum 1-5000ths of an inch. Gulliver, a high authority, places the average human red corpuscle 1-3200. The Medico-Legal Society of France, in 1873, 1-3257; Wormley, 1-3250; Masson, 1-3257; Formad, in 1888, 1-3200. All unite in the statement that b. The Mouse. the human corpuscle is larger than those of the domestic animals. fresh These are measurements upon blood, which has not been allowed to dry on animal or vegetable stuffs. 80 Red Blood Corpuscles magnified 319 diameters. a. The Cow. c. The Ox. Fig. 9 b. The Dog. Red Blood Corpuscles magnified 319 diameters. a. The Horse. c. Common Fowl. b. The Sheep. The average diamater of the red corpuscles of the blood of the sheep is 1-5000, the goat 1-6366, and these are so much smaller than those of man that a microscope of low power would certainly discriminate them by the size of the red corpuscle from those of man, as also those of the horse, 1-4600; the cow, 1-4500; the cat, 1-4004; the pig, 1-4230; and the mouse. 1-3814. Vide figs. 7, 8, 9. The greater difficulty arises with those animals whose red corpuscles approximate nearer in size to those of man, such as the dog. Taylor says the average diameter d. Salamander. of the red blood corpuscles of the dog are 1-3540; Reese, 1-3500; Formad, 1-3580; Wormley, 1-3561;"Gulliver, 1-3532. Micrometry Blood Corpuscles Side by Side, Magnified 500 Diameters. Dr. William J. Lewis, of Hartford. in a scholarly inaugural address as President of the American Society of Microscopists, delivered in August, 1889, says of the dog: ་་ 'Unfortunately in the dog the red corpuscles so closely resemble those of man that it is difficult to distinguish between them. "Out of two hundred corpuscles from the blood of man, and an equal number from a dog, Dr. J. P. Bradwell found that those measuring 1-3200 of an inch, forty-six were from the man and six from the dog. Of those measuring 1-3300ths of an inch, thirty-seven were from the man and seventeen from the dog. Of those measuring 1-3400 of an inch, fourteen were from the man and twenty-three from the dog. It will thus be seen that although the average human blood corpuscles is slightly larger than that of the dog, the variations in size overlap in measurement so as to make it unsafe to express a positive opinion when the question is confined to distinguishing between human or dog's blood. The blood of the guinea pig is still more difficult to determine in comparison with that of man. "From careful measurement of the red corpuscles in a given specimen, if found to average the same as those of man, a positive opinion may be expressed that the blood did not come from the sheep, ox, horse, pig, or goat, the corpuscles in those animals being so much smaller as to render the distinction easy." Prof. Reese, now perhaps one of our highest American authorities, claims that Dr. Richardson has demonstrated the possibility of distinguishing between human blood and that of the horse, cow, sheep, pig, and goat, with certainty and precision. That by employing very high microscopic powers, such as 1-30th of an inch objective, magnifying with a micrometer eye-piece over 3000 diameters, the human red blood corpuscle appears about 9-8ths of an inch in diameter, whilst those of the ox and sheep are about 5-8ths of an inch in diameter, indicating a very obvious difference in their respective sizes, and that the use of the ordinary powers (500 or 600 diameters) fail entirely to recognize the difference.(Reese Medical Jurisprudence and Toxocology, p. 132, 2d Edition Text Book, 1889.) Since the researches of Dr. Richardson great advances have been made by able observers, and it is now generally believed, that with a skilled and careful microscopist, and a good instrument of high powers, it will generally be possible to diagnosticate a human blood stain from that of any of the lower animals, with the possible exception of the guinea pig and the opossum. This, however, has not yet been conceded by some very high authorities, both American and European. In 1880 Prof. Reese, as editor of the 8th American Edition of Taylor's Medical Jurisprudence, Philadelphia Edition, said: "Prof. Richardson's microscopic investigation of blood stains are now always conducted with powers much higher than those mentioned by the author. (Taylor, speaking of powers of from 300 to 500 diameters.) I have examined with him blood stains from man, the pig, the ox, and the sheep, with powers varying from 1200 to 1800 diameters, and can testify to the obvious differences which unequivocally distinguish human blood |