When strong Nitric acid comes in contact with the skin it destroys the upper layers and turns them yellow, but as it coagulates their albumen it to a certain extent forms a barrier against its own further action, its action therein differing from that of Sulphuric acid. When swallowed it acts as an irritant poison; when its fumes are inhaled it may destroy life by suffocative spasm of the glottis or by intense bronchitis. It is used in old-school practice as an escharotic for warts and warty tumours; for phagedaenic ulcers, chancres, poisoned bites. The dilute acid is used internally in fevers to quench thirst; in bronchitis and phthisis to diminish the excessive secretions; in some cases of syphilis; in phosphaturia. It has even been injected into the bladder in a dilute form to dissolve calculi (Brunton). In the light of provings and poisonings all these uses are seen to have more or less specific relationship. "Phthisis," "syphilis," and "warty growths" represent Hahnemann's three miasms, Psora, Syphilis, and Sycosis; and Nit. ac. belongs almost equally to all three. But in addition to its miasm relationship, Nit. ac. has drug relationships of great importance. It is one of the chief antidotes of Merc., and it is in cases of syphilis that have been overdosed with Merc. that its action is most brilliant. I have known it do equally well when used after over-dosing with Kali iod., whether in syphilitic or non-syphilitic cases. In phthisical cases it follows the action of Kali c. in homoeopathic practice. In sycotic cases Thuj. follows it well. The localities in which the action of Nit. ac. is very strongly marked are—(1) the muco-cutaneous orifices and adjoining parts. Burnett made a brilliant cure of actinomycosis with Nit. ac. 3x in a patient who had been the round of the London consultants, and had doubtless taken much Kali iod. The localities in which the disease manifested itself, the region of the mouth and anus, gave Burnett his indication. The mouth (especially its angles) and anus are prominent seats of syphilitic action, and also of the action of the other miasms, the condylomata and fissures of sycosis; the fissures, fistulae, haemorrhoids, and sore mouth of psora. The right eye, the male genitals, and the bones are other localities for which Nit. ac. has a very strong affinity. In his directions about this remedy Hahnemann makes the remark that it is rarely required by patients who suffer from constipation. In my experience this is absolutely wrong. Constipation, as the symptoms of the Schema would indicate, is a prominent indication for Nit. ac., and I have cured almost as many cases with this as with any other single remedy. I have generally found, when I have had an opportunity of testing them, that Hahnemann's positive directions are thoroughly trustworthy; but his negative directions are quite as likely to be wrong as right. The characteristic discharges of Nit. ac. are offensive, thin, excoriating; if purulent they are a dirty yellowish green, not laudable pus. Ulcers have profuse exuberant granulations, and bleed easily. The dressing causes bleeding, and every touch causes "sticking pain as if from splinters." This is a grand keynote of Nit. ac., and will serve to indicate it wherever it is found. It requires a touch or movement to elicit it. When it occurs in the throat it requires the act of swallowing to set it up; in the anus, the passage of the stool; in ulcers, the touch of a dressing. It may occur from touch in any part of the body; in abdomen; in Ingrowing toe-nails. In the phthisical cases calling for Nit. ac. the chest walls are extremely sore to touch; there is sudden rush of blood to chest; hectic; frequent haemorrhages, bright red, profuse; sharp stitches through right chest to scapula. Great dyspnoea, cannot talk for getting out of breath; morning hoarseness; cough tickling, seems to annoy all night; at times loose and rattling; loud râles through chest; sputa offensive, bloody, purulent, dirty green; exhausting diarrhoea; exhausting sweats towards morning, chilly; heat in flashes or only on hands and feet. The suffocating effect of Nit. ac. fumes is an indication of its affinity for the respiratory organs. Here is an example (H. W., xxiv. 537): A two-gallon bottle of Nitric acid in the store of Mr. Harold Woolley, of Manchester, had become fractured. Water was thrown upon the bottle, and whiting placed about it to neutralise the fumes which issued from the fracture. Mr. Woolley superintended the process, and was in contact with the fumes for two hours. This happened in the afternoon. Next day Mr. Woolley complained of being unwell, and although medical aid was promptly summoned he died at five o'clock in the afternoon, death being attributed to "rapid congestion and inflammation of the lungs, in consequence of inhaling the fumes."—Nit. ac. is indicated in typhus when pneumonia supervenes; and when haemorrhage from the bowels occurs. The stools are green, slimy, offensive, may be purulent; the haemorrhages are profuse and bright red. With diarrhoea there is rawness and soreness of anus; the stool is putrid; in children may contain lumps of casein. Slimy stools, from excess of mucus passed with much straining. Or they may be (especially in scrofulous children) pale, pasty, sour, offensive. A keynote of Nit. ac. stools, whether loose or constipated, is pain after stool. There is pain during stool as if anus and rectum were torn and pierced, and violent pains after stool, lasting for hours. All the other orifices of the body are affected by Nit. ac.: Chancres and herpes about penis and prepuce; growths about vagina and cervix; leucorrhoea, immediately after menses; flesh-coloured, stringy, offensive. The nose, ears, and eyes are also influenced, and Nit. ac. is one of the first remedies in syphilitic eye affections, as iritis. Among the haemorrhages of Nit. ac. is haematuria. Goullon published a case in Archiv., ii. 36. (New Series), translated by Mossa, Rev. H. Française, ix. 136. A painter's apprentice, 15, after gilding an object, was seized with vertigo, with coldness, and soon with violent pain in bladder region. Next day he passed pure blood, bright red, with frequent strangury; the urine separated itself distinctly from the blood. During short intervals the blood did not flow. Tongue white, swollen. Nit. ac. 3 one drop was given, and in twenty-four hours the boy was cured. The urine of Nit. ac. affords one of the most important of all its keynotes: Urine of a strong odour, like horses'; or extremely offensive. Whenever this occurs as a concomitant in any case it is likely that other symptoms will point to Nit. ac. Fetid sweats on feet, hands, or in axilla no less point to Nit. ac. Among the haemorrhages of Nit. ac. are those occurring in cachectic women after confinement or abortion. H. N. Coons (Amer. Hom.) records the case of an anaemic woman, four weeks after miscarriage, had constant pelvic haemorrhage, at times coming with a gush; constant heavy feeling, much < standing or walking. Nit. ac. 2x, 20 drops in three ounces of water, a teaspoonful every two hours, quickly arrested bleeding and cured. As showing the value of peculiar symptoms, D. C. Perkins relates (Amer. Hom., xxii. 12) the case of a woman who said she was very ill, but could only describe her illness by saying that she" felt like a pulp-mill." Nit. ac. has "borborygmus as if a boiler was working in the bowels," and Nit. ac. proved to be the remedy. The sensitiveness to touch runs through the entire symptomatology, including the symptoms of the mind. The mind is weak, no ideas; if she exerts her mind thoughts vanish. Mind easily affected, inclined to weep. Hopeless despair. On the other hand, there is nervous excitability (especially after Merc.—-it is the excitable form of mercurialism that Nit. ac. best meets); peevishness; irritable, quarrelsome; fits of rage and cursing; inveterate ill-will unmoved by apologies. The head is sensitive to the slightest jar; to the rattle of waggons in the street, or even to the step of one walking across the floor. The head is very sensitive, even to pressure of hat; sensitive to combing, and on part lain on. Eruptions and ulcers bleed easily when touched. Eyes are sensitive to light. The ears present an exception, for deafness is > riding in a train or carriage. Sensitiveness of the head while out driving and stopping suddenly. The tongue is sensitive even to soft food. Nit. ac. is suited to: Persons of dark, swarthy complexion, with black hair and eyes; lean persons of rigid fibre; brunette rather than blonde nervous temperament. Persons suffering from chronic diseases who take cold easily and are disposed to diarrhoea. Old people with great weakness. Hydrogenoid constitutions. Peculiar sensations are: As if head in a vice from ear to ear over vertex. As if some one were forcibly pressing head; head tightly bound; constricted by tape; contused. As of a gathering in left temple. Pain as from splinters in eruption. As if warm water were flowing from and over eyes (first right, then left). As if teeth soft and spongy. As if abdomen would burst. As if a boiler working in bowels. As if a band round bones. As if dogs were gnawing flesh and bones, and as if sinews were being pulled up. As if ball of great toe had been frozen. As if splinters in great toe; in carbuncles, &c. Cramp-like pains, stinging, shooting, burning, pressure, and soreness. Excessive physical irritability, hysteria. Pains, even slight ones, affect him violently. Prostration, sick feeling, faints from least motion. Epilepsy > riding in carriage. Left-sided paralysis. Twitchings in various parts; frequent starts in upper part of body. Easily takes cold. Emaciated. Tedious suppuration. A characteristic accompaniment of Nit. ac. is "Profuse sweat breaks out on hands and feet." When this occurs in spinal injuries Nit. ac. is the remedy (B. Simmons, H. P., ix. 327). W. M. James (Med. Cent., vi. 325) cured this remarkable case: A girl had frequent attacks of petit mal, sometimes as many as fifty a day between the periods. At the beginning of the menses she had spasms so violent that they dislocated both humeri. Nit. ac. 200 given persistently put an end to the attacks, gradually. The first few times after commencing Nit. ac. there were spasms but no dislocation. Mohr (H. R., xiii. 210) gave Nit. ac. 3x to a man who suffered from cancer of the liver with bloody diarrhoea, followed by constipation; violent pains in stomach and liver; unable to sleep; or unable to take any food without much pain, mostly vomiting. Nit. ac. removed the pain and relieved the constipation entirely, and the patient died without an hour's suffering from the time he received Nit. ac. J. H. Fulton cured with one dose of Nit. ac. 200 R. M., 28, who had had bleeding piles for eighteen months. He had frequent bloody and slimy stools; but always bright red blood after stools, from a dessertspoonful to half a teacupful. When the stools were hard there was much pain in passing them. Burning in anus after stools (Med. Adv., xxxiii. 268). The symptoms are < by touch; pressure (of hat); > riding in carriage. < Eating (during and after eating, sweat). < Milk and fat food. < Exercise, exertion, effort, raising. arm, walking, standing. < Exerting mind. Lying down > headache. Night-sweat on parts lain on. Many symptoms come on towards morning. Cannot sleep after 2 a.m. Cough < on rising, during day, and at bedtime. Many symptoms, including bone-pains, come on in night. Warmth and cold both <. Warm weather < haemorrhoids; covering up = night-sweats. Least exposure = chills. Cold or warm things = tearing and shooting in teeth. Washing = warts to bleed. Cold weather < chilblains. Cold water > warm water feeling in eyes. Winter < chronic cough; hiccough; chilblains.