3. A small number of rounded or oval cells, about the size of leucocytes, containing one, or sometimes two small round nuclei.
4. Prostatic calculi. These are an inconstant constituent, but are very frequently met with after repeated coitus. According to some observers they are derived also from the bladder and urethra. They are distinguished by their yellowish colour, their irregular form (sometimes triangular, sometimes rounded or oval), and by their characteristic structure. They are composed of a substance arranged in concentric laminæ, which in the centre has a granulated appearance; they often exhibit one or more oval nuclei.
5. Spermatozoa in countless numbers.
In exceptional cases we find as additional morphological elements, especially in elderly people, scattered erythrocytes, cylinder-epithelium cells, and masses or granules of yellow pigment.
The spermatozoa are about fifty micromillimetres in length. Two parts may be distinguished in each, a head and a tail. The head, four or five micromillimetres in length, is flattened, and differs in apparent shape—though generally more or less pear-shaped—according as to whether it is seen sideways or on the flat.
The tail, which is about forty-five micromillimetres in length, narrows from before backwards. The fine posterior extremity is said to contain the contractile element, so that it is upon this portion that the familiar movements of the spermatozoa depend (Fig. [61]).
The spermatozoa are made up of a substance very rich in sodium chloride, and strongly resistent to reagents and to putrefaction. In consequence of their richness in mineral constituents, the ash, when they are calcined, retains their original form.
The movements of the spermatozoa can be properly observed only in fresh, pure semen (Fig. [62]).
If freshly ejaculated semen is treated with water, the movements of the spermatozoa very shortly cease, and their tails become rolled up in a spiral form.
