PRACTICAL EXERCISES 



203 



and take out the ligature. Wash the wound thoroughly with cor- 

 rosive sublimate, then with sterile (boiled) water, and close it, the 

 muscles being first brought together by a row of interrupted sutures 

 and then the skin by another row. Since it is difficult to thoroughly 

 disinfect the hair-follicles, and a suture passed through a septic 

 follicle is apt to give rise to suppuration, subcutaneous stitches 

 i.e., stitches passed by a curved needle through the deep layer of the 

 skin without coming through to the surface may be employed. 

 The wound is to be protected by a coating of collodion. No other 

 dressing is required. The animal is now removed from the holder 

 and put back to its hutch. The student must examine it at least 



FIG. 96. ARTIFICIAL SCHEME TO ILLUSTRATE A METHOD OF MEASURING THE 

 CIRCULATION-TIME. 



B, bottle containing water, the rate of outflow of which is regulated by screw- 

 clamp a; S, syringe filled with methylene-blue solution, connected with T-piece 

 A; M, beaker containing methylene-blue solution; b, c, screw-clamps; C, T- 

 piece, inserted in the course of the flexible tube E, and connected with the glass 

 tube T, which is filled with beads ; F, outflow tube. The clamp c having been 

 closed and b opened, the syringe is filled with the methylene-blue solution ; b is 

 then closed, c opened, and a definite quantity of the solution injected into the 

 system. The time from the beginning of injection till the appearance of the blue 

 at G is measured with the stop-watch. 



once a day for the next week, and study the differences between the 

 two ears (p. 159) and the two pupils. 



29. Determination of the Circulation-time. (a) Begin with an 

 artificial scheme (Fig. 96). Fill the syringe with a 0*2 per cent, 

 solution of methylene blue. Allow the water to flow from the bottle 

 by loosening the clamp. Inject a definite quantity of the methylene- 

 blue solution, and with a stop-watch observe how long it takes to 

 pass from the point of injection to the end of the glass tube filled 

 with beads. Make ten readings of this kind and take the mean. 

 Then raise the bottle so as to increase the rate of flow of the water, 



