494 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The process of trepanning and inserting the key-piece is somewhat 

 more complicated in the case of eggs that have already been incubated, 

 as the egg and the fluids employed must be kept warm. A water-bath 

 is required, consisting of a low tin box, filled with water, and provided 

 with covered apartments for the reception of the egg, the thin white, 

 the carbolic acid, and the salt solution, which are in this way maintained 

 at a proper temperature. In other respects, the mode of procedure is 

 exactly the same as given above. 



The key-piece may be removed as often as desired, provided the 

 above precautions are taken each time in inserting it. If the key-piece 

 is unscrewed by means of the fork and wrench, it must, of course, be 

 washed in the warm carbolic acid, and the vent cleared by the intro- 

 duction of a wire. The egg must be placed in the incubator with the 

 embryoscope on one side. If it is placed upward the respiration of 

 the embryo is hindered. The embryoscope can be turned up at any 

 moment, and kept upright for five minutes at a time without injury to 

 the embryo. "With a little practice the whole process of arming an egg 

 with the embryoscope may be completed in from six to eight minutes. 



The embryoscope is well adapted for purposes of class-demonstra- 

 tion, for investigating the growth of the various parts of the embryo, 

 and the physiological processes during embryonic life, as the action of 

 the heart, movements of the body, &c. It is indispensable to the study 

 of the effects of external agents upon the embryos of warm-blooded 

 animals, and must be of great service where it is required to determine 

 the precise stage of development before removing the embryo from the 

 egg. It has been found useful in studying the formation of double 

 embryos. Fenestrated eggs have been successfully incubated up to the 

 thirteenth day, and it is probable that, under favourable conditions, the 

 embryos of such eggs would reach maturity. 



On the fifth day it is still easy to bring the embryos under the 

 window. On the sixth and seventh days it is more difficult. At this 

 period the change in the position of the embryo, which requires from 

 five to ten minutes, should take place in the incubator. 



After the eighth day the embryo cannot be brought under the 

 window. If it be necessary to determine whether such an egg or an 

 older one still lives, we have only to leave the egg for several hours in 

 the incubator with the window directed up wards a little, after which, by 

 strong reflected light, one may readily see the blood circulating through 

 the channels of the vascular area.* 



Curtis, J. S. — The Quantitative Determination of Silver by means of the Micro- 

 scope. 



[Describes a " micrometer measuring apparatus," consisting of a Microscope 

 with a vertical and two horizontal cross hairs and a mechanical stage.] 



6th Ann. Bcp. U.S. Geol. Survey, 1885, pp. 323-52 (1 pi. and 2 figs.). 

 Malassez, L. — Sur quelques nouveaux Appareils. II. Hemochromometre perfec- 

 tionne. (On some new apparatus. II. Improved hfemochromometer.) 



Arch, de Physiol, VIII. (1886) pp. 261-8 (2 figs.). 

 Net, O. — Magnesiumlampen. (Magnesium lamps.) 



[The magnesium ribbon is unrolled from a wheel at the back of the apparatus, 

 and there is a patent adjustment for the burner which removes the ash by 

 means of a clockwork motion with brushes, rollers, revolving discs, or some 

 such mechanism. Three kinds are figured, one representing the lamp in the 

 form in which it can be used directly with suitable lenses or mirrors for 



* Of. Dr. C. O. Whitman in Amer. Natural., xxii. (1888) pp. 186-90 (2 figs.). 



