or other signs of circulatory failure following injudicious attempts to reduce a high pressure.

The same condition obtains in a failing cardiovascular system, when the pressure has been for a long time high. (See chart, Fig. 44.) Here also we may have most serious and distressing symptoms, pointing to circulatory failure, and yet the pressure may be found still above the estimated normal level.

FIG. 44.-Hypotension of lost compensation (relative hypotension). Arteries markedly sclerosed, heart showed myocardial degeneration, pulse always rapid. Cerebral symptoms marked, treatment had very little effect.

(d) Secondary or Temporary Hypotensions.-All other cases presenting an abnormally lowered systolic pressure should at present be placed under this head. Etiologically these cases will be found singly or combined to be due to cardiac, vasomotor, actual muscular or of blood volume or composition changes.

G. M. Piersol1 has conveniently grouped the several causes as follows:

1. Hypotension due to vasodilatation, shock and collapse from whatever cause.

2. Acute infections and toxemias.

3. Hypotension due to cardiac weakness, as in chronic myocardial degeneration, acute dilatation, arteriosclerosis and chronic nephritis.

4. Orthostatic albuminuria and amyloid disease, not associated with true nephritis.

5. Advanced cachexias, occurring in the course of carcinoma, diabetes and nephritis.

6. Hypoplasia of the chromaffin system as in Addison's disease.

7. Hypotension due to diminished blood volume as in cholera, persistent diarrhea, dysentery, cholera infantum, Graves' disease and hemorrhage.

8. Certain nervous affections, of which paresis and epileptic coma are examples, also true neurasthenia.

9. Drug poisons, as tobacco. This ordinarily raises bloodpressure, with the apparent anomaly that heavy smokers frequently have subnormal pressures. For the effect of drugs on blood-pressure, see Chapter XXIII, page 409.

10. There are many examples met with of the so-called gouty or rheumatic manifestations of lumbago, sciatica, or neuritis which show a blood-pressure somewhat below normal. Many of these cases have a subnormal acidity of the urine, and are liable almost constantly to a copious deposit of phosphates which leads to, or is accompanied by, a state of nervous depression.

1 Penn. Med. Jour., May, 1914, xvii, No. 8.

Extreme Low Pressure.-The lowest blood-pressure in an adult compatible with life has been reported by Neu to be from 40 to 45 mm., and this only occurred with subnormal temperature accompanied by unconsciousness. He has observed and recorded recovery after a temporary fall in pressure as low as 50 mm.

Pressures of 80 to 95 are not uncommon, and may persist for long periods, to be followed finally by a recovery of normal values.

Effects and Danger of Hypotension.-The direct effect of a falling blood-pressure is the accumulation of an abnormal amount of blood in the veins, and a slowing of the current in the arteries. This will affect the capillary circulation and interfere with the nutritive and secretory processes which depend upon it. The most serious effect is on the heart, as it has been shown that complete loss of vasomotor tone soon leads to death, because of the gradual accumulation of nearly all the blood in the body on the venous side, so that the heart has no blood upon which to act.

CHAPTER XVI

HYPERTENSION; HYPERPIESIS

The term hypertension, is generally applied to any condition in which the blood-pressure is maintained at a level above normal, irrespective of the degree or duration of the elevation. Such use of the term admits of confusion and doubt in the mind of the reader, because of the diversity of conditions included in so comprehensive a term. The fact that careful clinicians continue to report cases with hypernormal blood-pressure, in the absence of either cardiac or nephritic degenerative changes, and since we are able to obtain a permanent and lasting return to normal blood-pressure values in certain cases by appropriate treatment and hygiene, it would seem to justify an effort to limit this term and to admit the presence of such a clinical entity, having as a prominent symptom, a transitory elevation of systolic pressure; for if we fail to recognize this clinical condition, there will remain an unfilled gap in our clinical conception of cardiovascular and renal pathology.

That we may accept this condition as a pathologic and clinical entity, is shown by the fact that its existence is recognized by many modern authorities, among them Janeway,1 Butler, R. A. Torrey, T. C. Janeway, and H. W. Cook.5

2

1 Am. Jour. Med. Sci., 1906, cxxxi.

2 The Practitioner, 1909, lxxii.

3 Penna. Med. Jour., April, 1914.

4 Jour. A. M. A., Dec. 14, 1912, lix, p. 2106.

5 Jour. A. M. A., Jan. 28, 1915, lxiv, No. 4.

Definition of Hyperpiesis or True Hypertension. It would seem best, at least for clinical purposes, to limit the

FIG. 45.-Hypertonia vasorum; upper line, section of normal artery middle, section of contracted artery; lower, section of artery restored to it natural partial contraction. (L. F. Bishop, in Medical Record.)

term hyperpiesis or true hypertension, to a well-recognized symptom-complex in which the rise in systolic pressure is moderate and persistent, but not permanent, and to