was written about the characters of the mucus corpuscle and the pus corpuscle, and the importance of distinguishing them from one another. The so-called mucus corpuscle, however, is nothing more than an epithelial cell, often somewhat altered, entangled in the viscid mucus, which is formed in greater or less quantity upon the surface of all mucous membranes. A small quantity of mucus derived from the genito-urinary mucous membrane entangling a few small cells of epithelium, is always found in healthy Urine. These cells, however, vary in size: they are more transparent than the pus corpuscle, and their granular character is less marked. Such cells, when acted upon by acetic acid, entirely disappear, or they become much more transparent. In some of them a single nucleus may be perceived. The pus corpuscle, on the other hand, when treated with this re-agent, swells up, becomes perfectly clear and transparent, while from one to four small highly refracting corpuscles come into view.

This change is shown in fig. 2, where some corpuscles will be observed containing only one of these bodies, others two, and some three or four. Half the figure is magnified 215, and the other half 403, diameters.

This change distinguishes pus from everything else. It should, however, be borne in mind, that after pus has remained for some time in Urine, the corpuscles become softened, and their characters less distinct; but in such a case, should there be any doubt as to the nature of the deposit, we must resort to a chemical examination.

For the chemical characters of pus, see Tables for the Examination of Urine.

Blood corpuscles are often much altered by remaining in Urine. In alkaline Urine the blood retains its red colour, but the normal acid of Urine renders the colouring matter brown, whence the smoky appearance of acid urine which contains blood.

The corpuscles are often found to be much smaller after they have lain for some time in Urine. The cor

PLATE XXI.

VARIOUS URINARY DEPOSITS.

Fig. 1. Pus and blood corpuscles, with crystals of triple phosphate, in the Urine of a man suffering from fungus growths connected with the mucous membrane of the bladder.

Fig. 2. Spermatozoa and cells of vaginal epithelium removed from the vagina of a little girl, a few hours after a rape had been committed.

Fig. 3. Crystals of triple phosphate, many of which closely resemble octohedra of oxalate of lime, with epithelial casts, and casts containing oil from the Urine of a case of chronic nephritis, with partial fatty degeneration. Fig. 4. Deposit of phosphate of lime in an amorphous form, from the Urine of a man who was suffering from an attack of sick headache.

Fig. 5. Large crystals of uric acid, with a number of octohedra of oxalate of lime from the Urine of a boy, aged 18, suffering from diabetes. The crystals formed after the Urine had been allowed to stand for 8 or 10 hours.

Fig. 6. Penicilium glaucum and oxalate of lime, crystals of uric acid crystallized round a hair, from the Urine of a patient suffering from chronic bronchitis and emphysema, and habitually passing large quantities of uric acid.