HARDWICKE'S SCIENCE-GOSSIP. 



197 



slightly thinner than the object. (See a, fig. 127.) 

 These are as supports for the cover, to prevent its 

 unduly pressing on the specimen, which it should 

 just touch, in order that the balsam may not wash 

 it away. Put on the cover, secure it with a clip, 

 and let the balsam run under by capillary attraction. 

 Leave the preparation two or three days before 

 taking off the clip, and then you will find that you 

 have a slide with no air-bubbles, with the object not 

 onfy in the centre, but also not flattened, nor yet 

 reduced to a glass-like transparency by the agency 

 of heat. All these desirable points have been 

 attained with far less trouble than if a cell had 

 been used. Spinnerets look as well in glycerine as 

 in balsam, not to say better, only it is more trouble 

 to mount them in this medium because it necessi- 

 tates the use of a cell. I should mention that the 

 balsam used must be liquefied by the addition of 

 chloroform or benzine : I prefer the latter. 



Fig. 127. Diagram illustrative of the method of mounting 

 spinnerets, showing how they are to be arranged on the slide, 

 and how the glass cover is to be prevented from unduly 

 pressing them, by being supported on three bits of cover- 

 glass (a). 



The demonstration of the silk-glands requires a 

 little care, and I have never yet prepared a slide 

 that I am proud of. The reader will more easily 

 understand the description which follows if he will 

 examine fig. 128, which shows where the silk-glands 

 are to be sought for. It will be seen, that, taking 

 up so much space as they do, there is no chance of 

 overlooking them. As the figure is only meant to 

 indicate the position of the silk-glands, I have not 

 verified, by copying from a fresh dissection, the 

 exact position and shape of every organ, and 

 although it represents the interior of the abdomen 

 fairly well, I do not pretend that it is quite accu- 

 rate. After many trials, I find that, on the whole, 

 the following method gives the best results. First 

 sever the abdomen from the cephalo-thorax, and 

 then skin it, leaving only the pulmonary chambers 

 and spinnerets in situ. The organs shown in fig. 128 

 cannot yet be seen, being hidden by the liver, which 

 occupies the greater part of a spider's abdomen, 

 and in which the other parts are mostly imbedded. 

 This and the heart must be carefully taken off, and 



the eggs (if any) removed. The dissector will now 

 have the breathing, part of the digestive, and all 

 the silk-secreting apparatus exposed to view. As 

 we are only treating of the last, we will pass the 

 others by. Spiders have arteries but no veins, 

 therefore the silk-glands are not attached (by blood- 

 vessels) to any part, but lie free, bathed in the 

 blood, from which they derive the elements of their 

 secretion. They must be carefully disentangled 

 from the other organs, taking care that the large 

 glands, described in the June number at pages 

 134-5, and shown at c, fig. 123, are not left behind. 

 The spinnerets are to be divided as in fig. 126, with a 

 pair of scissors, and the two sets carefully separated 

 without pulling off the glands which belong to each. 



Fig. 128. Section of a Spider's abdomen, showing the position 

 of the silk glands in relation to the other organs: a, 

 Spinnerets ; b. Silk-glands ; c, Large glands ; d, Pulmonary 

 leaflets; e, Pulmonary chamber ;/, Heart; g g, Pericardium; 

 h h. Vessels by which the blood is returned to the heart ; 

 1, Alimentary canal ; k, Anus; I, Ovary, containing eggs-. 

 m, Termination of the oviduct. 



They should be soaked in common acetic acid for 

 about three days, which will make them transparent, 

 and afterwards washed and allowed to soak in 

 distilled water, which should be changed two or 

 three times to make sure that no acid remains. It 

 is necessary to stain the glands in order to bring 

 out the nuclei of the epithelial cells, the ducts, and 

 other minuter parts. There are many staining 

 fluids in use, among which I may mention carmine, 

 hematoxylin, and anilin-blue. Ilecipes for these 

 may be found in any book treating of the prepara- 

 tion of medical objects. The spinnerets and glands 

 must be mounted in a cell with glycerine ; Canada 

 balsam is simply "ruin" to the glands. 



A few words respecting mounting webs may not 

 be out of place. Not many are sufficiently inter- 

 esting to be permanently preserved, but a few (the 

 web of Cinifio in particular) are worth the trouble. 

 They should mostly be mounted dry, and to get the 

 web nicely spread out on the slide, the glass slip 

 should be taken to the web and not the web brought 

 to the slip. Rough-edged slips are the best to use , 

 because the web catches in the edges. A Ciniflo's 

 web may be stained, if previously wetted with 

 alcohol. It must not, however, be removed from 

 the slide where first placed, for it cannot be spread 



