136 



THE ART OF MAKING MICROSCOPE SLIDES 



S. S. mouse 



but may also occur during staining; the 

 center of many an excellent section has 

 become detached from the slide simply for 

 the reason that it has been handled in 

 aqueous stains. The nuclei are not so 

 clearly shown by carmine as by many 

 other stains, but for valuable material the 

 author has always used Smith as an in- 

 surance policy against losses. It is also 

 easy with this stain to distinguish the 

 various cells since the cell membranes 

 themselves pick up the blue while the mass 

 of the^^yolk retains the yellow of the picric 

 acid. 



Gregg and Puckett, on the contrary, 

 take the sections down to water in the 

 usual manner and then stain them in 

 Delafield's hematoxyhn [Chapter 20 DS 



11.122 Delafield (1885)] differentiating in 

 acid alcohol in the manner indicated until 

 the nuclei alone remain clearly stained. 

 They are then counterstained in eosin- 

 orange (Chapter 20 DS 12.222 Gregg and 

 Puckett 1943) before returning through 

 the alcohols to xjdene and then to the 

 mountant. The author has never had the 

 least success in staining amphibian em- 

 bryos with hematoxylin because of the 

 very strong affinity of this stain for the 

 albumen granules in the j^olk. 



After staining the sUdes are cleaned and 

 labeled in the usual manner and will show 

 almost incredible improvement over the 

 usual "Bouin's fixative-hematoxylin-eo- 

 sin" technique which most modern em- 

 bryologists appear to employ. 



Preparation of a Sagittal Section of an Entire Mouse 



This preparation is not recommended to 

 the stern and dedicated research worker, 

 whose onh' interest in the preparation of 

 microscope slides is to demonstrate a the- 

 sis, but has been included for the benefit 

 of those who, like the author, enjoy mak- 

 ing a beautiful slide for its own sake. It 

 may, of course, be argued by those who 

 have to justify themselves that such sec- 

 tions form an admiral^le method of demon- 

 strating the main relationships of mam- 

 malian anatomy to a large class. It is 

 proposed, in fact, to prepare a sagittal 

 (vertical-longitudinal) section of an entire 

 mouse from the tip of its nose to the very 

 last joint of its tail. This is a feat of great 

 technical difficulty and requires atten- 

 tion, at odd moments, during several 

 months. The author does not think that 

 the end can justify the means: the 

 beautiful preparation must be its own 

 justification. 



The mouse selected for the preparation 

 should be of such a size that the section 

 will fit onto a standard 3-inch by 1-inch 

 slide, but sufficiently old to be covered in 

 hair. A litter of freshly born white mice 

 should, therefore, be watched until the 

 young arc completely clothed with hair; 

 this will be between one and two weeks 

 after birth. The next problem is to kill and 

 fix the mouse in such a manner as to fulfill 

 the conditions that the tail shall \)v 

 straight, so that it can be included in a 



sagittal section, and that the fixative shall 

 shall be able to penetrate to all parts. The 

 tail must, of course, be curled under the 

 body if the section is to be placed on a 

 slide, and it must also be attached to some 

 rigid structure so as to remain straight. It 

 is desirable to kill the mouse in a relaxed 

 condition: and injection of sodium amytal 

 is probably the best. For those who do not 

 have access to h3'perdermic syringes and 

 reagents of this tj^pe, however, it is quite 

 satisfactory to kill with ether (not chloro- 

 form which stiffens the animal rapidly) 

 though one has less time to work before 

 rigor mortis sets in. Before kilUng the 

 mouse one should have secured the finest 

 possible needle obtainable and some very 

 fine silk, not Hnen or cotton, thread. There 

 is only one way of insuring that the tail 

 shall coincide with the nose and that is to 

 sew the two together. Therefore, as soon 

 as the mouse is dead, open the jaws and 

 insert a little wedge of wood so that they 

 are partly opened (at the tip of the jaws 

 the gap should be about 2 mm.) and then 

 proceed to pull the tail around until the 

 tip of it projects just beyond the nose. 

 Using the fine needle and the fine silk 

 sew the skin from each side of the tail to 

 each side of the nose. It must be remem- 

 bered that we are concerned only with 

 getting half a dozen perfect sagittal sec- 

 tions and that anything outside the exact 

 central plane will not show. Now take a 



