(C) Hydrophobia

In this disease the symptoms indicate irritation of certain nerve centres, and a greatly increased reflex irritability. The centres irritated are chiefly those of the medulla oblongata and spinal cord, although delirium, indicating irritation of the cerebral cortex, is also occasionally present. The symptoms point mainly to the medulla oblongata; there are various spasms of the muscles of deglutition and respiration which occur to some extent spontaneously, but are also evoked by slight sensory stimulation. The mere sight of water gives rise to the idea of swallowing it, and brings on a violent spasm of the muscles of deglutition. A breath of cold air on the surface of the body causes a violent respiratory spasm or gasp. The centres in the cord are also irritated, as shown by the tendency to spasm of the muscles generally.

An irritating virus is present in the blood and induces these conditions of the nervous system. Pasteur's researches have proved that the virus is present in the cord and medulla. After death manifest ngns of irritation are usually visible on microscopic examination. They are to be found most characteristically in the medulla oblongata and next to that in the spinal cord, but are not absent in the other parts of the nervous system. The most prominent condition is an accumulation of leucocytes around the vessels in the substance of the cord and medulla oblongata. There may be just a few leucocytes in the sheath, but from this there are all gradations up to a condition in which the vessel is clothed with a mantle consisting of many layers of leucocytes (Fig. 330). The leucocytes are also present elsewhere, and sometimes in such quantities as to induce some observers to speak of the collections as miliary abscesses. The leucocytes find their way into the pericellular spaces and are found keeping company with the ganglion cells in these situations. In the medulla oblongata the main nutrient vessels are towards the posterior part, and as the motor nuclei are in this region, it may be that the localization of the irritation here is partly determined by their proximity. In addition to these conditions minute haemorrhages have been observed in the medulla and cord.

A blood vessel from the medulla oblongata in a case of hydrophobia.

Fig. 330. - A blood-vessel from the medulla oblongata in a case of hydrophobia. Large numbers of round cells are seen in its sheath, x 350.

Signs of irritation are present in other parts of the body besides the nervous system. The salivary glands have been found to present abundant leucocytes between the glandular elements (Fig. 331). In the kidneys also there are signs of irritation in the form of dilatation of vessels and haemorrhage.

It is clear then that here an intense irritant, presumably the toxine of a microbe as yet undiscovered, is circulating in the blood, and the intensity of it may be judged from the fact that all these very marked appearances occur within two or three days of the onset of the nervous symptoms. These structural changes vary greatly in degree in different cases, being sometimes very slight. This would indicate that the virus attacks the nerve structures directly, and that the inflammatory appearances are concomitants and not necessary parts of the morbid process. They are, however, evidences of the presence of a strong irritant.

From the salivary gland in a case of hydrophobia.

Fig. 331. - From the salivary gland in a case of hydrophobia. In the middle is portion of a duct; abundant round cells surround it as well as the glandular structure, shown in outline, x 350.

(D) Tetanus

The microbe of tetanus has been already described at p. 356. It produces whether in artificial cultures or in the body a toxine of the most extraordinary virulence in its action on the nervous system. The symptoms are those of an intense irritation of the spinal cord and medulla oblongata. There is violent spasm of the muscles, but those under the control of the medulla oblongata are not so specially involved as in hydrophobia, although the person frequently dies from spasm of the muscles of respiration.

There are signs of irritation discoverable in the spinal cord and medulla oblongata, although they are very different from those in hydrophobia. In tetanus the most prominent and constant appearance suggests the exudation of fluid from the vessels. The fluid sometimes collects around the vessels and, as in hardened specimens the albumen is coagulated, a granular appearance is produced. In other cases it looks as if the fluid produced a disintegration of the neighbouring nervous tissue, the appearance being that of the "granular disintegration" of Lockhart Clarke. The localization of the disintegration around the vessels suggests its origin in an exudation from them. tare is also usually an excess of leucoeytes around the vessels and in the grey substance of the medulla oblongata generally.

The presence of an irritant as the cause of tetanus was inferred long before the discovery of the microbe, and the disease was in this view grouped along with hydrophobia. In both of these diseases the temperature is elevated, and, especially in the case of tetanus, reaches sometimes a most startling height (110° F.). It is-difficult to account for this extreme rise of temperature by the muscular spasm, though the possibility of this explanation is not to be absolutely denied. It seems more probable, however, that the irritant acting to some extent generally on the tissues is the cause of the elevation of temperature. The analogy to the specific fevers is seen in the facts that tetanus has been known to occur in epidemics, and that if a case survives eight days there is considerable probability of recovery, as if the poison ran its course in that period.

Literature

Abscess of brain - Gowers, Dis. of nervous syst., ii.; Leberth, Virch. Arch., x., 1856; Billroth, Arch. d. Heilk., 1862; Kettelheim (Abscess from empyema), D. Arch. f. klin. Med., 1885, xxxv.; Eiselberg, ibid., xxxv.; Macewen, Pyogenic infective diseases of the brain and spinal cord, 1893; Adams (Mode of extension from ear), Glasg. Med. Jour., 1881, xv.; Barker, Barr, Greenfield, Coats, etc., ibid., 1887, xxviii., 119; Ballance in Allbutt's Syst. of Med., vii., 1899. Sclerosis - Charcot, Lectures on dis. of nerv. syst., Syd. Soc. trans., 1st series, 1877; Marie, Lects. on dis. of spinal cord, New Syd. Soc. transl., 1895; Rindfleisch, Virch. Arch., xxvi.; Leyden, Deutsch. Klinik., 1867; Erb, in Ziemssen's Encycl., 1877, xii.; Moxon, Guy's Hosp. Rep. 1875, xx.; Coats, Glasg. Med. Jour., 1879, xii. Acute febrile conditions - Popoff (Typhoid), Virch. Arch., lxxxvi.; Schule, ibid., lxvii.; Letzerich, ibid., lxxv.; Blaschko, ibid., lxxxiii.; Middleton, Jour, of Anat. and Phys., Oct., 1880. Dementia paralytica - Bayle, Gaz. des Hop., 1854, No. 77; Bevan Lewis, A text-book of mental diseases, 1899; Obersteiner, Virch. Arch., lii.; Meyer, ibid., lviii.; Lock-hart Clarke, Lancet, 1866; Crichton Browne, West Riding As. Rep., vi., 1876-Hydrophobia - Allbutt, Path, trans., xxiii., 72; Benedikt, Virch. Arch., xiv.;. Gowers, Path, trans., xxviii., and Dis. of nerv. syst., 2nd ed., 1893; Coats, Med. Chir. trans., lxi., 1879; Ross, Path, trans., xxx., 1879. Tetanus - Leyden, Virch. Arch., xxvi., 1863; Lockhart Clarke, Med. Chir. trans., xlviii., 1865; Dickinson, ibid., Ii., 1868; Coats, ibid., lxi., 1878; Allbutt, Path, trans., xxii., 1871.