224 MICROSCOPICAL MEMORANDA. 



Dissecting Instruments to use with the Microscope. A small scalpel 

 with a thin and narrow blade, whose edge is curved backwards, and 

 two common needles, very sharp, and fitted into handles like that of 

 the scalpel, are all the instruments required for the microscopic dissec- 

 tion of organs. The scalpel is used for dividing, and the needles for 

 separating and clearing the parts, and for bringing them into contact 

 with the re-agent employed, or into the field of the microscope. A few 

 small hooks may also be provided, attached to threads having a small 

 leaden weight at the end, for the purpose of stretching membranes 

 which are submitted to observation. When the object under examina- 

 tion is immersed in an acid, small wires of platina are used in place of 

 needles. 



Dropping Tubes. These are glass tubes drawn out to a capillary 

 opening at one end by the lamp ; and they are used for placing on the 

 object-holder a drop of the re-agent whose action is to be examined, 

 and which has been introduced through the same end by sucking. 

 They may be prepared very easily by heating the middle of a piece of 

 glass tube till it be softened sufficiently to be bent, and after it is cold, 

 applying the flame of the lamp to one of the branches at a short dis- 

 tance from the bend. When it is quite red hot, laying hold of the two 

 ends, they are to be drawn asunder, when the softened part will be 

 drawn out till it becomes capillary ; and if broken off at a convenient 

 length, it will be found pervious. Raspail's Organic Chemistry. 



Harrison on Transverse Strife on Navicula Hippocampus. In our last 

 number we noticed the existence of distinct longitudinal striae on this 

 species of Navicula. Our attention has since been directed to transverse 

 striae on the same species by Mr. Harrison of Hull. We can with him 

 testify their presence, after some considerable patience and manipula- 

 tion as regards the modification of the light. They are more evident in 

 the single shell, not mounted in Canada balsam, than in the slide in which 

 they are set up in that menstruum. 



Grimelli on the Vascular Structure of the Iris. In the Annali Univer- 

 sali, 1841, M. Grimelli has published an article on the structure of the 

 iris. By injections of coloured oils thrown into the carotids, he has 

 been able to inject the interior of the eye, and all the vessels of the iris. 

 During his injection he has seen the iris swell, and from his observations 

 on the direction and form of these vessels, he believes that that mem- 

 brane is of a vascular, and not of a muscular structure. Lond. and E din. 

 Month. Jour. Med. Science, Jan. 1842, p. 58. 



[If we mistake not, the late Sir Astley Cooper demonstrated this fact 

 some years since ; the specimens are, we believe, still to be seen in the 

 Museum left by that distinguished anatomist.] 



Busk on the Hairs of Animals. The references to the figures in 

 Plate 2, will be given in the continuation of Mr. Busk's paper " On the 

 Structure of Hairs and other Cuticular Appendages in various classes of 

 Animals. No. 2, page 225. 



