Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: LESSON III. BLOOD CORPUSCLES OF MAN. STRUCTURE. COUNTING. 1. With a sharp needle prick the finger either at the tip, or a few millimetres from the root of the nail (the finger should be perfectly clean); touch with the centre of a cover-slip the drop of blood which issues; lower the cover-slip on a slide. Observe the red corpuscles. a. They roll about readily when the cover-slip is lightly touched. Soon after being taken from the body they stick to one another, and, owing to their shape, usually in rouleaux. 6. They are biconcave discs. Note that on focussing down on the circular face a darkish centre and a light rim is first seen and then a light centre with a darkish rim: when viewed in profile and the centre focussed they appear somewhat dumb-bell shaped. c. They appear homogeneous, their colour is like that of the red blood corpuscles of the frog (cp. Less. II. § 1, c). d. Towards the outside of the drop, where evaporation is going on, many of the red corpuscles are crenate. e. They are much smaller than the red corpuscles of the frog. 2. Observe the colourless corpuscles. Most are larger than the red, they resemble in general appearance the white corpuscles of the frog; to observe their amoeboid movements a drop should be protected from evaporation (Less. n. § 2, e) and warmed to the temperature of the body. Irrigate with -5 p.c. acetic acid (cp. Less. II. § 5). a. The red corpuscles swell up and become spherical, their hemoglobin is dissolved, leaving the hardly visible stroma. (The same effect is produced by water.) b. No nucleus is brought into view. c. In the white corpuscles the cell-substance becomes more transparent, and the nucleus comes into view (cp. § 3). 3. Prepare two dry films of blood (cp. p. 14). Place the cover-slips fi...