22 PRACTICAL HISTOLOGY. 



which are recognised by their branching and forming a network are stained red, while the 

 ivhite fibres are but slightly acted on by the magenta. This preparation need not be pre- 

 served. The observer is not to suppose that the corpuscular elements do not exist before the 

 addition of a reagent ; they do exist, but, owing to their refractive index being so near that of 

 the fluid in which they are examined, they are not visible until some staining reagent is added. 

 It is further to be remembered that the relation of the fixed corpuscles to the white fibres is 

 changed in a teased preparation. Occasionally large oval granular and nucleated cells are 

 found, especially along the course of the vessels ; they are the so-called plasma cells. 



(b~} Dilute Acetic Acid. Make a similar preparation, and irrigate it with a one per cent, 

 dilution of acetic acid. 



EXAMINATION (H). Note that, as the acetic acid displaces the salt solution, it acts 

 upon the white fibres and causes them to swell up, to become transparent, so that they appear 

 quite homogeneous and jelly-like, though they are not dissolved. Some of the fibres may, 

 however, present annular constrictions in their course. This clearing up of the white fibres 

 brings the other elements in the tissue more clearly into view to wit, the elastic fibres and 

 the corpuscles. The elastic fibres are highly refractive, and their branches unite to form a net- 

 work, and if such a fibre be broken across it curls up at its ends, though otherwise they pursue 

 a straight course. Numerous fusiform or oval nuclei are revealed ; they are the nuclei of the 

 fixed connective-tissue corpuscles, whilst the small bi- or tri-partite nuclei belong to the lymph- 

 corpuscles. The acetic acid may be displaced by magenta solution, when the elastic fibres 

 and the nuclei are stained of a bright red colour (PI. IV., Fig. 4). Do not preserve this. 



AREOLAR TISSUE. 



PERMANENT PREPARATIONS OF AREOLAR TISSUE. 



PREPARATION (a). With a small subcutaneous syringe (fig. 27) forcibly inject a quantity 

 of a half per cent, solution of osmic acid under the skin of the groin of a young dog, rat, or 



rabbit just killed, until an artificial 



FIG. 27. cedema or bulla is formed. After half 



an hour, snip open the bulla, taking 

 care that no hairs get into it. With 

 scissors snip off a small piece of the 

 distended connective tissue and place 

 it on a slide. Spread it out as a mem- 

 brane with needles, and add picrocar- 

 mine. It will require several hours 



Subcutaneous syringe for interstitial injections, and the cannula. The to Stain, and to avoid desiccation add 

 hollow needle ought to be made of gold, to prevent acids from actinc r 



on it. Natural size. a small drop of glycerine and cover. 



When it is sufficiently stained, remove 

 the picrocarmine, and substitute glycerine containing a trace of formic acid. 



(K) A similar preparation may be stained with logwood which acts in a few minutes ; 

 remove the logwood solution and mount in glycerine. 



(c) Instead of injecting osmic acid, the subcutaneous injection of a saturated watery solution 

 of picric acid does very well. Stain the section with picrocarmine, as directed under (b) . 



