ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 415 
rod, if used in a class, soon becomes, together with the students, in a 
most deplorable condition. 
C6) Miscellaneous. 
The Microscope in the Workshop.* — Prof. W. A. Rogers calls 
attention to the advantages to be derived from the use of the Microscope 
in the ordinary operations of machine construction. 
The two objections generally urged against its adoption are, that a 
special and expensive machine, mounted on a foundation separate from 
the building, would be required for its use, and that without special 
appliances an adequate illumination of metal surfaces could not be 
obtained. 
The author considers that both these objections may be met. 
With regard to the first it is only necessary to have the Microscope 
firmly clamped to any machine with which it is to be used. The form 
of mounting used by him has been found to be well adapted to the 
purpose. It is found that with powers of from 100 to 200 the images 
in the Microscope are remarkably steady. 
The second objection is met by the use of the prism illuminator 
invented by the late R. B. Tolies. This prism is mounted just at the 
back of the objective. The light meeting a plane face passes to a 
facing, making with it an angle of 45°, where it is totally reflected and 
passes out nearly parallel with the axis of the lens. 
The author gives twenty-four examples of operations in which the 
Microscope may be advantageously employed. 
Bloocl and Blood-stains in Medical Jurisprudence. f — Mr. Clarke 
Bell gives a summary of the present state of scientific knowledge on the 
subject of the identification of blood and blood-stains. The red blood- 
corpuscles afford the best means for discriminating between the blood of 
man and other animals. 
Three methods of investigating blood have been employed, viz. 
(1) chemistry; (2) the spectroscope ; (3) the Microscope and its allies 
the micrometer and the photomicrogram. 
No chemical differences have been discovered between the blood of 
man and of other animals. 
The Microscope, however, has shown that the human corpuscle is 
larger than those of most of the domestic animals. 
The average diameter of the human red blood-corpuscle is 1/3200 
in.; that of the sheep 1/5000; the goat 1/6366; so that these can 
be easily distinguished under the Microscope ; as also those of the horse 
1/4600, cow 1/4500, cat 1/4004, pig 1/4230, and mouse 1/3814. 
There is greater difficulty with animals such as the dog, whose red 
blood-corpuscles more nearly approximate in size to those of man. 
Prof. Formad has, however, recently claimed that by the use of very 
high magnifications, up to 10,000 times, obtained by rephotographing 
single corpuscles of different animals, he has obtained the following 
measurements. The human corpuscle was enlarged to 3J in. in diameter, 
guinea-pig to 3 in., dog to 2f in., ox to 2^ in., sheep 2 in., and goat 
If in. 
* Proc. Amer. Micr. Soc., xiv. (1893) pp. 128-31. f Tom. cit., pp. 91-120. 
