252 THE AMERICAN MONTHLY [Sept., 



a pipette the separated and stained cells, put a drop on the slide, 

 and apply the thin cover carefully. 



For filamentous tissues, the foregoing should be modified. 

 The best method is to dissociate by fine forceps. A piece of 

 tissue being placed in the dissociating liquid, the ends of a fila- 

 mentous fascicle are seized by forceps and slowly torn in two. 

 This is repeated on the pieces obtained until we have a small 

 bundle containing a few filaments. Mount on the slide ; stain 

 and cover. 



Dissociation by Interstitial Injection. — (Ranvier method). 

 Fill a hypodermic syringe with the liquid, either osmic acid (1 

 part to 1000), the i alcohol, or iodised serum. Pierce the organ 

 with the canula and force in the injection. If the tissue is com- 

 pact, separation is finished by needles or by forceps, in a small 

 quantity of the fluid used ; if the tissue is loose, like subcutane- 

 ous tissue, the injection will form a rounded swelling. With 

 curved scissors cut off a bit of the enlargement and add the thin 

 cover. The movements should be rapid, or the liquid will flow 

 away, the elements become scattered, and the injection will 



have produced no useful effect (Ranvier) This is the 



preferable method for studying loose connective tissue. 



PART II. — APPLIED TECHNIQUE. 



Loose Connective Tissue. — The best is the subcutaneous 

 cellular tissue. Remove a large piece of skin, preferably from 

 the fold at the groin where the subcutaneous layer is abundant, 

 and place the subcutaneous layer upward, taking care not to 

 entangle hairs in it, and with a hypodermic syringe gently in- 

 ject picro-carmine into the tissue. It forms a rosy swelling 

 ... of gelatinous consistence. With curved scissors cut off a 

 slice and discard it. Cut from the freshly reddened tissue a sec- 

 ond piece as small as possible, rapidly put it on the slide, add a 

 little picro-carmine, cover and examine. The subcutaneous 

 tissue of the dog is well adapted to this. 



Connective Tissue Bundles. — The foregoing preparation 

 will show these and the elastic fibres. In 2 or 3 hours it will 

 be strongly colored ; . . . then run under the cover a drop of 

 glycerine with 1 per cent of acetic acid. The connective tissue 

 bundles will swell, be decolored and here and there show Heule's 

 spiral fibres stained red. 



