268 NOTES AND MEMORANDA. 



exhibitcrl to the meeting, and its utility shown by centring a slirle 

 which had been eccentrically mounted for the purpose. — QueJcett Club 

 Journal, April, 1872. 



An Improved Mode of Observing Capillary Circulation. — Mr. H. 

 L. Smith says that if we grasp a frog in the hand and plunge it in 

 water about as warm as can be conveniently borne, say about 120^, 

 though he has never measured this, judging simjily from the apparent 

 warmth to the hand, we shall find that, in a few moments, the frog 

 will become perfectly rigid ; it may now be removed and laid upon 

 a plate for dissection. Carefully opening and stretching the parts by 

 pulling upon the fore limbs gently, or even cutting the bones if 

 necessary, the heart may be displayed, showing the contraction and 

 expansion beautifully; and if now the animal is placed in warm 

 water, the lungs will immediately float out, and by a suitably contrived 

 stage the circulation may be examined. " It is better, however, not to 

 do this, but to draw out gently the large intestine by means of blunt 

 forceps, and then spreading the mesentery on the glass of the frog- 

 plate (I find it convenient to use a large one with an elevated glass, 

 instead of one in the same plane, on which to spread the mesentery) 

 we can observe the capillary circulation very nicely with a :^th or 

 ^th inch objective, by dropping a bit of thin glass over the placo 

 or with a higher power ' immersion.' Of course the parts opened 

 must be kept moist and covered with a cloth, and a few drops of tepid 

 water added from time to time. If the experiment has been properly 

 conducted, the animal will remain perfectly qiiiet and the circulation 

 will continue for hoiirs ; I cannot say how long, for I have never 

 known it to cease until long after I had finished all the exhibition 

 I have ever had occasion to make. If the frog is a large one, the 

 mesentery can be spread out so as to afford the most magnificent 

 exhibition of capillary circulation, with a distinctness, and under an 

 amplification which will excite the greatest admiration and astonish- 

 ment in anyone who has only seen it hitherto in the web, or the tongue. 

 The objectives of a high power ought to be more tapering at the end 

 than our American makers usually furnish them. In this respect 

 some of the foreign objectives are superior. It would be very little 

 more trouble to make the higher powers at the object end but little 

 larger than the front lens, and thus infinitely more convenient for 

 work than with the large flat surface which most of them now present. 

 In fact, with a -^th or ^V^^^ American objective, as ordinarily made, it 

 would be impossible to approach sufficiently near to the mesentery to 

 focus on the smaller caj)illaries without striking some of the larger 

 blood-vessels. If nothing more could be done, the front set at least 

 might be mounted in a little projecting tip or nose, and if those who 

 are ordering objectives will insist upon this, I doubt not the opticians 

 will do their part." 



The New Erecting Arrangement. — A writer who signs himself 

 C. S., writes as follows to the ' American Naturalist ' (April) : — In the 

 January number of the ' Monthly Microscopical Journal,' Dr. Ward 

 describes " a new erecting arrangement especially designed for use 



