External

Both boric acid and borax have the power of destroying micro-organisms and are thus disinfectant and antiseptic, but their value is slight, and they are much more active in preventing than in inhibiting decomposition. The action is extremely local. Solutions of boric acid will relieve itching. Neither substance produces any irritation. Boric acid is very largely used to preserve milk, butter and animal food.

Internal

Borax and boric acid check the action of saliva on starch, but, if anything, they increase the action of the gastric juice and the pancreatic secretion. Large amounts, however, slightly retard digestion, and still larger are gastro-intestinal irritants. Boric acid is rapidly eliminated in the urine, it is said to increase the urea and the quantity of urine. Large doses increase the acidity of this fluid. It is also excreted in the saliva, sweat, and faeces, and it is stated in rare cases to cause abortion. In exceptional instances where large quantities have been applied to raw surfaces or mucous membranes, reduction of temperature, depression of spirits, feeble pulse, ecchymoses and vomiting have supervened. Harmful symptoms do not follow from taking food preserved with boric acid if the amount used is small, such as anything under one-tenth of one per cent., but they may follow if large amounts are used. It should never be used for solid foods.

Therapeutics of Boric Acid and Borax

As they do not irritate, both these substances are largely used to keep wounds, ulcers, and sores sweet. The action is so local that they cannot be used to dress cavities. Boric lint is employed to dress wounds. It is made by passing lint through a hot saturated solution of boric acid. Boric cotton is made the same way. Lister's boric acid ointment consists of boric acid, 1; white wax, 1; paraffin, 2; almond oil 2 parts. A saturated solution of boric acid (4 per cent.), or the glyceritum boroglycerini well diluted with water may be used as an antiseptic wash. Such solutions are used for ozaena, vaginitis, urethritis, and ophthalmia. Colitis is often benefited by washing out the large bowel with a quart 960 c.c of a saturated solution of boric acid; sometimes tannic acid is added. Lister's ointment, or an ointment of boroglyceride, (not official) glycerin, 92; boric acid, 62; by heating, may be used for pruritus, sunburn, etc. Powdered boric acid blown into the ear is very useful in foetid discharges from it. Thompson's fluid (borax, 1; glycerin, 2; water, 2), in the proportion of 1 to 8 of warm water, is commonly employed to wash out the bladder in cystitis. One of the most important antiseptic solutions is that of Thiersch. This consists of boric acid, 12; salicylic acid, 2; water 1000. The glycerin of the B. P., which is, borax, 1; water, 2; glycerin, 4; and the honey of borax, of the B. P., which is, borax, 2; glycerin, 1; clarified honey, 16; are excellent applications for aphthous states of the mouth, especially in children. The following is a good wash for the mouth: Glycerin of borax, see above 6; tincture of myrrh, 1; water to 48.

Borax has been given in epilepsy, and its use is gaining ground. It is often prescribed with advantage in combination with bromides, but it is decidedly inferior to them, although in exceptional cases it may succeed when they have failed. As it is an antiseptic it has been given internally in typhoid fever and phthisis, but with doubtful benefit. Taken internally, it is said to relieve irritability of the bladder. In rare cases its use has caused either psoriasis, a papular eruption especially marked near the elbows, an erythematous rash, or eczema. Nausea, loss of appetite, vomiting, and diarrhoea may be produced. It has no effect on the intelligence. The taste is best covered with syrup of orange peel.

Boric acid is not employed internally in medicine, excepting for correcting the foetor of fermentative dyspepsia and in ammoniacal cystitis, where it is also used in solution for irrigation of the bladder.