Fig. 173. - Normal pulse-tracing of a patient suffering from aortic regurgitation and angina pectoris.

1 These experiments were made with Rana temporaria.

I knew from unpublished experiments by Dr. A. Gamgee, that nitrite of amyl had this power, and therefore tried it on the patient. My expectations were perfectly answered. The pain usually disappeared in three quarters of a minute after the inhalation began, and at the same time the pulse became slower and much fuller, and the tension diminished. Occasionally the pain would disappear, though the pulse regained its normal fulness, and on these occasions the pain always reappeared after the lapse of a few minutes (Fig. 174). Whenever the pulse again regained its normal character completely (Fig. 175), I knew that the pain would not again return.

Fig. 174. - Tracing of the same pulse during severe anginal pain.

Fig. 175. - Tracing of the same pulse during temporary relief of pain by nitrite of amyl. The pain returned after a few minutes.

In some cases of angina pectoris nitrite of amyl has failed. One reason of this may be either that the drug has not been pure, or that it has undergone changes from age. In one case mentioned to me by Dr. Balfour, the patient was only relieved by nitrite of amyl newly made, the drug appearing to lose its power in a few days. As migraine is generally connected with vascular spasm, I employed the nitrite of amyl in headache, and found that frequently, though not invariably, it relieved the pain. It was also useful in neuralgia of the scalp. As epilepsy has been supposed to depend upon spasmodic contraction of the cerebral vessels, I employed it in this disease, during the fit, without success, but Sir Crichton Browne found that when administered immediately after the appearance of the aura it prevented the fit which would otherwise have come on. On the commencement of the cold stage in ague nitrite of amyl cuts short the attack. In sea-sickness, a disease probably of cerebral, rather than gastric, origin, it appears to give relief. It has been employed to aid circulation in cases of syncope, and in chloroform poisoning, its administration in the latter case being combined with the depression of the patient's head below the level of his body, and the use of artificial respiration. In spasmodic asthma it sometimes affords some relief, but this is not very marked. It is useful in the case of persons who are subject to sudden flushes of heat and profuse perspiration.

The administration of nitrite of amyl is not attended with much danger. I have pushed it in many cases, and have seen no bad effects from its use. In cases of chronic bronchitis and emphysema, however, it is advisable not to give it even for the relief of asthmatic attacks which come on in this disease, as the difficulty of breathing already present may be seriously increased by the action of the drug upon the blood. It has been thought that its administration would be especially dangerous in aortic disease; and no doubt it is well both in this disease and in other cases to give the drug in the recumbent posture and thus avoid the faintness which might otherwise occur. Although it causes a feeling of fulness in the head, little danger of apoplexy is to be apprehended from it, because the blood-pressure, instead of being higher, is much lower than usual, and therefore the tendency of the vessel to burst must be reduced to its minimum.

Nitro-glycerinum. Nitro-glycerine, Glonoine. C3H5(NO3)3. Not officinal.

Properties. - A colourless transparent liquid; aromatic taste.

Solubility. - It is slightly soluble in water, readily soluble in absolute alcohol and ether, soluble also in oils and fats.

Preparation. - By dropping pure glycerine into a mixture of sulphuric and nitric acid kept cool by ice; pouring the mixture into water; washing it well; and carefully drying in a warm room.

Dose. -- 1/200 to 1/50 gr. increased to 1/10 grain; of Liquor Nitroglycerini (non-officinal) 1 (1 gr. in 100 min. rectified spirit), 1/2-10 minims.

B.P. Tabellae Nitro-glycerini. Tablets of Nitro-glycerine. Tablets of chocolate, each weighing 2 1/2 grains, and containing 1/100th of a grain of pure nitro-glycerine.

Dose. - or two tablets.

liquor Nitro-glycerini (non-officinal)1 (1 gr. in 100 rectified spirit), 1/2-10 min.

Action. - Its action is much like that of nitrite of amyl and other nitrites,2 but is more persistent. In frogs it causes at first great restlessness, then lethargy, to which convulsions and paralysis succeed. In mammals it causes depression, with very rapid pulse and respiration, paralysis of reflex action and voluntary motion, loss of sensation, and death by stoppage of the respiration. It agrees with nitrites in acting as a poison to muscle. The spinal cord appears to be paralysed before the cerebral ganglia, and the convulsions in frogs are of cerebral rather than spinal origin. It paralyses the heart of the frog when directly applied. It diminishes the oxidising power of the blood and communicates to it a chocolate colour, like nitrites, and like them also it lessens the blood-pressure. In some persons it produces intense headache, even in exceedingly minute doses. It is curious that its action upon the blood and organs should so exactly resemble that of nitrites, because nitro-glycerine is a nitrate and not a nitrite of glyceryl. Hay has shown, however, that nitro-glycerine is decomposed by alkalis, two-thirds of its nitric acid being reduced to nitrous acid and uniting with the alkali to form a nitrite, whilst the remaining third is set free without reduction and forms a nitrate.

1 Martindale and Westcott, The Extra Pharmacopoeia.

2 Lauder Brunton and Tait, St. Bartholomew's Hospital Reports, 1876, p. 140

The reasons why nitro-glycerine acts more powerfully than nitrites probably are that the whole of it is absorbed without decomposition, and that nitrous acid being set free in the blood in a nascent condition is more active than it would otherwise be.

Uses. - Like nitrite of amyl, it is useful in angina pectoris, headache, neuralgia, epileptic vertigo, and epilepsy. Its action being more persistent than that of nitrite of amyl, it is sometimes more efficacious. It is sometimes of service in spasmodic asthma, uraemic asthma, and in puerperal convulsions. It frequently relieves sea-sickness, and may lessen pain in gastralgia and hepatic colic. By dilating the vessels it may cut short or prevent the cold stage of ague. By lessening the arterial tension and diminishing the resistance the heart has to overcome, it is useful when the heart is weak in old persons, or from fatty degeneration, or where the tension is abnormally high, as in Bright's disease. In conjunction with elaterium it is said to have proved useful in myxoedema.

B.P. Liquor Sodii Ethylatis. - Vide p. 619.