BY DR. KLEIX. 47 



in the liquid, and are difficult to seize upon with the needle. 

 On the other hand care must be taken, as the liquid evaporates, 

 to add more, so as not to allow the preparation to become dry. 

 In the preparation of tissues which consist of several parallel 

 bundles, such as nerves, tendons, or muscular tissue, our object 

 is to divide the fragments in the direction of the fibres into 

 smaller and smaller portions. Even when the tisstie consists 

 of elements which tend in no particular direction, it is still 

 desirable to follow one direction in teasing the object being 

 best attained by first fixing the fragment with one needle, then 

 piercing it with the other held in the opposite direction, and 

 finally drawing the two apart. It is further noteworthy that 

 the teasing must be performed on the centre of a slide, and 

 limited within an area which is not larger than the cover-glass. 

 The drop of fluid in which the preparation is to be mounted 

 should be placed on the cover-glass, which must then be in- 

 verted upon it. As the liquid evaporates it must be renewed 

 from time to time. 



Action of Acetic Acid on Fibrous Tissues. In a 

 teased preparation of tendon in salt solution, bundles of very 

 fine homogeneous-looking fibres are seen. If the preparation 

 is irrigated with weak acetic acid the bundles are seen to swell 

 out, become homogeneous, and completely disappear. If con- 

 centrated acid is used the effect is more rapid. 



Areolar Tissue. In a portion of fresh mesentery (of a 

 frog or of a small mammalian animal) spread out on a glass 

 slide and mounted in salt solution, we have the shining wavy 

 bundles forming a felt-work. In the omen turn or pleura of a 

 guineapig or of a cat, prepared in a similar way, the arrange- 

 ment is that of a meshwork. From each larger bundle we see 

 several smaller ones splitting off, and then meeting with simi- 

 lar ones which are branches of other larger bundles in the 

 neighborhood. (See Fig. 8.) According to the abundance of 

 these collateral or secondary bundles, and the way in which 

 they run, the meshes vary in size and form, being round, rhom- 

 bic, or oblong. 



Effect of Maceration. For the purpose of macerating 

 fibrous tissue, ten per cent, solution of common salt, lime water, 

 baryta water, or solution of permanganate of potash may be 

 used. By all these reagents the interstitial albuminous sub- 

 stance is dissolved out, so that the bundles split into their con- 

 stituent fibres. All that is then necessary to display them is 

 to prepare a small fragment with needles. Diluted bichromate 

 of potash solution may also be used, but its action is very slow. 

 Elastic Tissue. Elastic tissue is characterized specially 

 by the facts that the elementary fibres of which it consists do 

 not swell in ackls, that they do not yield gelatin in boiling, 

 and that in general they are 'not united into bundles, but occur 



