October, 1910. 



KNOWLEDGE. 



415 



In seeking information upon this subject in quite up-to-date 

 books, with a \ie\v to help in overcoming such a difficulty, one 

 is often ad\ised by the \ arious authors to make small cuts in 

 different positions ;tnd directions with sharp-pointed scissors : 

 others recommend the material to be steeped in alcohol oi 

 some other solution for a minute or so before placing in the 

 proper fixati\e. Workers in histology and c\-tolog\- are very 

 frequentl\' con\inced. on examining their finished preparations 

 and sections, that such methods as these are far from 

 successful, and \ery often most harmful, especially to small 

 objects. Cutting or snipping certain \ery small or entire 

 objects causes very distorted appearances when the sections of 

 same are examined under the microscope, especially those not 

 far removed from the cut surfaces. A very noticeable illustra- 

 tion in this direction is the testes of small animals. Hen 

 marked swelling in the seminal tubules, and changes in tht- 

 cells are more or less readily detected in areas some consider- 

 able distance from the cut. Testes, however, seldom give any 

 difficulty in sinking in any fluid, but are referred to as an 

 example of the bad effect caused by cutting ; whence it is 

 easy to understand that other small material may be affected 

 in a like manner. 



Steeping in fluids, such as alcohol, for even so short a tinn 

 as recommended by some, is far from a good method to adopt. 

 It will be readily understood that here, owing to the highl\- 

 penetrative action of alcohol, as well as its quick hardening 

 power, you have at least the first five or six external 

 layers of cells alcohol fixed and hardened, so preventing in 

 anj- marked or required manner the fvn-ther action and 

 penetration of fixatives possessing such small penetrating 

 power as liquid of Flemming, Lindsay Johnson, or the like. 



As I have often had to treat material presenting these 

 difficulties. I have many times considered what could be done 

 to overcome this annoyance. 



The following, I think, will appeal to many, and is a 

 method that occurred to me. and one that I have used with 

 great success in my laboratorv' for some time. 



Take cylindrical glass tubes ; those used for holding two 

 micro-slips back to back are very useful for the purpose, only 

 it is preferable if they are rather longer than usual ; about 

 four inches in height. Of course, when working with 

 fixatives, such as Flemming's strong and Lindsay Johnson's 

 platinum chloride solutions, where a bulk of liquid only four 

 or five times the volume of the object immersed is required, it 

 is not necessary to use such large tubes. 



At the bottom of these place a moderately thin layer of 

 clean, long-fibred, absorbent cotton wool. Do not use a 

 cheap wool, as this often contains a lot of short fluffy material, 

 which is annoxing and not satisfactory for the purpose. 



Now pour into the tube, until it is a little more than two- 

 thirds fuU, the fixative to be used : then put in your objects 

 to be fixed. T-il:r nimthrr piece of wool, and shape or fold in 



L^VEK OF WOOL 

 OBJECT BElNQ flXcO 



liquid, and continue the pressure until half the amount of 

 wool is inunersed. One or more air spaces will soon be 

 noticed, owing to the absorption of the liquid by the wool ; 



FIXING SOLUTION 



WOOL PLL'(j 



TROOiiH WiTn LftNER 

 OF FWNO 80LUTIOM 

 M T He ?,0TT0MTO 



such a manner that it will require a gentle pressure to push 

 into the tube, and will occupy about an inch in depth : press 

 this down into the tube until it touches the surface of the 





o&n^c ^cvo 



V< OOL PLUG 



OSnvCAClO VAPOUR 



Bjecr F(\eo ovi a 



GLASS NE.£DL£ WHICH 



15PUSHE0 INTO Tne 



BKSe OFTn£ CORK. 



these can be got rid of by pressing the plug of wool a little 

 further down. Pour a little solution on the top surface of the 

 plug, so as to be sure of complete saturation ; pour off what is 

 not absorbed ; invert the tube, when the objects will immedi- 

 ately pass to the opposite end and be entirely immersed. 



No fear need be entertained about any solution filtering 

 through or down the sides of the plug. To pre\ent e\aporaf ion, 

 gently cork the tube ; or the open end can be placed in a glass 

 trough at the bottom of which has been poured a little of the 

 fixative. 



.•\nother very useful purpose to which a slight modification 

 of the above may be put is to about half fill the tube with a 

 fluid to the fumes, of which it is wished to expose an object 

 such for example as the vapour of osmic acid. It is not 

 necessary in this case to put a layer of wool at the bottom, 

 but the wool plug must be inserted in exactly the same way as 

 previously described. 



On the base of a cork that will fit the tube tightly, place a 

 piece of clean white filter paper, and upon this place the object 

 which you wish to subject to osmic acid vapour; carefully push 

 the cork, with the object upon it, into the inverted tube. 



A better method, so as to be sure of all sides of the object 

 coining equally in contact with the fumes, is to push through 

 the middle of the cork a glass needle and upon the point of 

 this carefully press your object. 



The second figure will make the procedure quite clear. 



E. J. Shepp.\rd, F.R.M.S. 



SCALES OF HABROSTOLA TRI PLASI A.— This 

 species was not purposely selected as being typical in respect 

 of its scales, but it does happen to possess scales of the leading 

 types. Two of these txpes are here represented ; the figures 

 on the larger scale were made by the help of the 2mm. 

 immersion, the smaller ones with the 16mni. It was found 

 necessary to underexpose the plates ; better results may pro- 

 bably be obtained by using monochromatic light and a 

 specially sensitised plate, so as to hold back the background 

 and prevent it from exerting so energetic an action on the film. 

 It was curious to find that the 2mm. required only about 

 twice as long an exposure as the 16mm. The size of the 

 objects may be inferred from the fact that in the broader form 

 of scale here figured the transverse distances from each 

 longitudinal stria to the next, across the middle of the scale, 

 average nearly two micra. The larger or fan-shaped scales, 

 which are in shape somewhat similar to the leaves of Ginkgo 

 biloba (a specimen of botanical Latin which I cannot 

 altogether commend), are perhaps typical of the Xoctuina. 

 The smaller ones, of an elongate o\al shape, are interesting 

 because under a low power they show the " watered silk " 

 appearance. The undulating transverse lines which give rise to 

 this effect mav either be due to undulations of the surface of 



