Most of the substances used in medicine have a strong taste, and many a very unpleasant taste.

What is usually termed taste frequently depends on a mixture of taste and smell, and if the sense of smell is abolished for the time being, the characteristic taste of the substance cannot be distinguished. This is the reason why castor-oil, which owes its nauseous taste almost entirely to its odour, can be swallowed without being so readily distinguished if the nose is held during the act of swallowing. In addition to the taste they produce in the mouth, certain substances leave an impression termed ' after taste' on the tongue after they have been swallowed or ejected; and this is sometimes quite different from that of the taste of the substance itself: thus bitters leave a sweet after-taste in the mouth. If quinine is taken in a nearly neutral solution, it leaves a persistent bitter taste from the sparingly soluble alkaloid being precipitated on the tongue and remaining there for a length of time, but if the quinine be taken with excess of acid, so as to keep it entirely in solution, and washed out of the mouth immediately with a draught of water, it leaves a sweet after-taste.

Some substances after their entrance into the blood are excreted by the saliva and may cause a somewhat persistent taste in the mouth; this is observable in the case of iodide of potassium.

Iodine appears also to have the power of causing other substances to be excreted by the saliva, when they are combined with it, and thus Bernard found that iodide of iron was secreted by the saliva, though lactate of iron was not; and I have sometimes thought that iodine has a similar effect upon quinine, because I have very frequently noticed patients complain of a persistent bitter taste in their mouth when I have given quinine combined with iodide of potassium, although they did not complain of this when either of the drugs has been given without the other.