66 The Microscope. 



lected ; capillar}^ not venous, nor arterial. 3. Site of collection. 

 — The forearm, near the wrist. With some persons the fingertip 

 is a favorite place for collecting blood, but the fat and dirt found 

 there are objections, to say nothing of the needless pain of nerve 

 papillae puncture. If dirty, the forearm should be washed with 

 soap and water, or ammonia and water, and rubbed dry with a 

 clean towel previous to puncture. 4. Instrument for collecting 

 the blood. Codman and Shurtleff, Boston, Mass., prepared the 

 writer's scarificator, that can be buried to the depth desired with 

 a single sudden painless motion. It is desirable to obtain no 

 more nor no less blood than is suflScient to fill the space between 

 an ordinary cover glass and slide. This amount is a drop about 

 one-eighth of an inch in diameter. By thus preserving a uni- 

 formity in the size of the drop of blood as near as is possible, 

 one can form an approximate judgment of the comparative 

 number of corpuscles in diflferent specimens, and the relative 

 proportion of the serum to red and white corpuscles and of the 

 red and white to each other. Best to clean the scarificator point 

 by driving it into a clean towel after each use. 5. How to get 

 the blood. Having the forearm and the instruments ready, the 

 observer grasps the wrist with the left hand so that the skin is 

 drawn tense ; the scarificator in the right hand of the observer 

 is applied to the radial or ulnar edge, whichever is held upper- 

 most, avoiding veins, and the point is entered by approximating 

 the thumb and fingers holding the scarificator. The point then 

 pierces the skin so quickly as hardly to be felt, and if the capil- 

 lary circulation is good, the cut fills with blood and exudes. 

 Usually the sluggish circulation requires a squeezing of the cut 

 to make the drop exude. A clean scalpel is then used to scrape 

 off the blood and to transfer it to the slide, or the slide can be 

 touched to the drop directl}', when it is immediately covered and 

 transferred to the stage of the microscope, previously prepared. 

 6. Power employed. Objectives, ^ to tV inch; eyepieces, 2 or 

 1 inch. The writer uses Tolles'. 



What to look for in rheumatic blood. 1. Red corpuscles, 

 color, form, plasticity, adhesiveness. In rheumatism they are 

 generally sticky and adhesive, outlines winged, huddling to- 

 gether in ridges or irregular masses like frightened sheep in a 

 fold ready for shearing. They act as if their covering of 



