Squash Preparations from Solid Bodies 



General Principles 



Nature of the Process 



Squash preparations are not, as their 

 name might cause one to suppose, ob- 

 tained merely by crushing an organ or 

 animal in order that it may become thin 

 enough to examine under the microscope. 

 This would result in the hopeless distor- 

 tion of the cells and their contents. A 

 squash preparation, properly prepared, is 

 obtained by causing the cells of animal or 

 plant material to become separated one 

 from the other without losing their indi- 

 vidual shape in order that they may be 

 spread out on a shde in a single layer for 

 examination. This process is today much 

 better known in botany than in zoology, 

 though it was at one time the standard 

 method of preparing histological speci- 

 mens. Another fundamental difference be- 

 tween the smear and squash technique is 

 that the former always employs fresh un- 

 fixed material while the latter should 

 always employ- a material which has been 

 fixed previously. 



Process of Maceration 



The separation of cells of fixed plant or 

 animal material through the hydrolysis of 

 their interstitial tissue of cement is known 

 as maceration. It does not matter what 

 fixative has been used, though in the 

 author's experience fixatives containing 

 cln-omic or osmic acid, or mixtures of 

 these, are best. Tissues are fixed in the 

 ordinary way and the fixative thoroughly 

 removed ]:)y washing before maceration 

 commences. The two most common metli- 

 ods of maceration, either for animal or 

 plant material, are acid hydrolysis and 

 enzyme hydrolysis. Each will be described 

 separately. Acid hydrolysis of plant tissues 

 is almost always carried out in 10 % hydro- 



7G 



chloric acid, in ^vhich the fixed tissue is 

 soaked until a sample of it, placed under a 

 coversUp, is found to disintegrate into its 

 constituent cells when the coverslip is 

 tapped hghtly with a needle. Acid hydrol- 

 ysis of animal tissues, however, has been 

 carried out with almost any acid used for 

 microscop}^ and reference should be made 

 to Chapter 19 (V 40) where many sug- 

 gested mixtures are given. It may be 

 pointed out that almost any acid fixative 

 solution, if diluted with from 50 to 100 

 times its own volume of water, will act as 

 a macerating agent. 



Enzyme hydrolysis of animal tissues 

 may be conducted either in an alkahne or 

 an acid environment, and reference should 

 be made to the methods of Jonsset 1903 

 and Langeron 1942 for examples of each 

 of these. Abbre\dated techniques for these 

 methods are to be found in Chapter 19 

 under V 40 and need not be expanded here. 

 Enzyme hydrolysis of plant tissues is of 

 quite recent origin, and depends on the 

 extraction of enzymes from sources which 

 are customarily used in the digestion of 

 plant material. Ensweller 1944 (20540b, 

 19, 109) suggests the extraction of various 

 fungi but the method of Faberge 1945 

 (Chapter 19, V 41.1), of which a detailed 

 description is given in one of the typical 

 preparations following this chapter, is 

 much to be preferred. The terminal point 

 of enzyme maceration may be detected, 

 exactly as is that of acid maceration, b}'' 

 whether or not the organism or tissue 

 unrler examination disintegrates into its 

 constituent cells. 



Staining and Mounting Macerated 

 Specimens 



Though the process of maceration is it- 

 self quite easy, staining and mounting of 



