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anatomically very like that of the nose, there is nothing to prevent the supposition that something of the same kind takes place in the bronchial tubes. Riegel still further remarks that this theory fully agrees with the results of Lowen's experiments, which show that irritation of sensitive nerves causes by reflex action overfilling of the vessels inside the range of the irritated part. Stoerckt supports Weber's theory as regards the import of fluxion, but sides with Wintrich as a believer in the diaphragmal spasm, and is decidedly opposed to Biermer's theory of bronchial spasm. Amongst other theories of asthma may be remarked that Leyden 1 already in 1871 mentioned that the asthmatic attacks were caused by small oblong octahedral crystals, which mechanically (perhaps also chemically) irritated the peripheral ends of the vagus in the mucous membrane of the bronchials, and hereby caused by reflex action a spasm of the muscles of the small bronchial tubes. Similar crystals had already been observed by Friedreich and later on by Zenker|| in cases of bronchitis crouposa, Charcot and Forster also knew them from myxomatous tumours, and Neumann found them in leuchæmic blood and marrow. Meissen has furthermore found them in nasal mucus of a patient suffering from a cough and “ Stocksnupfen ” with asthmatic attacks, also in cases of phthisis, and Ungar also confirined Leyden's theory of crystals in the sputum of asthmatic patients, but maintains that they are not pathognomonic, but quite accidental.

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* Lowén, Ueber die Erweiterung von Arterien in Folge einer Nervenerregung. Arb. aus d. physiolog. Anstalt zu Leipzig, 1867, ref. von Riegel, l. c.

+ Stoerck, Mittheilungen über Asthma bronchiale, Stuttgart, 1874, p. 14, and following.

| Leyden, Zur Kenntniss des Asthma bronchiale, Berl. klin. Wochensch., 1871, p. 533. $ Friedreich, Virchow's Archiv, 30te B., 1864. || Zenker, Archiv f. klin. Medicin, 18te B., S. 125.

| Meissen, Ueber das Vorkommen der Leyden'schen Asthmakrystallen, Berl. Klin. Wochensch., 1883. p. 332.

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The theory brought forward by Curschmann in 1883 has about the same fate. Curschmanno considers a great many forms of reflex asthma to be caused by catarrhal affection in the finer bronchial tubes, which he named bronchiolitis exudativa. A characteristic of this disease is the presence of peculiar spiral threads (1-1 millimeter thick, and several centimeters long) in the sputum. The threads are casts of the bronchials, and are in direct relation to the asthma, which is caused by them through a secondary bronchial spasm. These spirals of Curschmann are meanwhile no more pathognomonic than the crystals of Charcot and Leyden, as they are also found in cases of fibrinous pneumonia (Vierordt, v. Jacksch, Vincenzo, Pel, see G. Sée).†

G. Sée in a critical review of previous theories comes to the following conclusions :-Asthma is a neurosis in the medulla oblongata, that is to say in the centre of respiration, caused by an acquired or native elevated reflex irritability in this organ. The cause of the attacks must be sought for in irritations, which originate in pneumogastric nerves or other peripheral nerves. The effect of the reflex exhibits itself in the motory nerves of the inspiratory muscles, specially those of the diaphragm. We have, therefore, before us a permanent neurosis, whose attacks are caused by an irritation especially of the pneumogastric nerves, and which is always concluded by a tetaniform contraction of diaphragm, this theory only (in contrast to the bronchial spasm) can explain the dilatation of the lungs, this, as above remarked, has already been mentioned by Sée in 1865. The principal factor in the asthmatic attacks is therefore not (as in the bronchial spasm) a direct motor effect of the pneumogastric

* Curschmann, Ueber Bronchiolitis exudativa und ihr Verhältniss zum Asthma, Archiv f. klin. Medicin, 32 B., 1883.

+ G. Sće, Krankh. der Lunge, III B., Einfache Lungenkrankh., translated from the French, Berlin, 1887.

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nerve, only the sensitive pneumogastric fibres take a part in this respect as they lead the irritation up to the noeud vital of the spine, whence the irritation spreads through the nervi phrenici to the diaphragm.

When the trunk of the pneumogastric or the central end of the cut nerve is irritated, the lungs expand from reflex influence through nervi phrenici (Riegel and Edinger).* This dilatation can therefore take place only when nervi phrenici are intact, which proves that the lungs expand indirectly through a spasm of the diaphragm. But besides the tetaniform contraction of the diaphragm, there must also be a reflex dilatation of the vessels in the bronchial mucous membrane in order to explain the expectoration; this Weber, as above mentioned, has already called attention to. It must therefore be assumed that an irritation proceeding from the lungs, at the same time extends itself (a) to the respiratory centre, from which the tetaniform contraction of the diaphragm originates, and (b) to the vaso-motor centre (also situated in the medulla oblongata), whence it spreads to the vaso-dilatorial nerves of the lungs, in other words to the place from which the irritation issues (Lowén).

Before we leave the theories of asthma, it must be remarked that Schmidtbornt has recently explained the asthmatic attack as being the expression of a reflex spasm of the arteries of the lungs, and that this by causing considerable obstacles in the blood circulation in the lungs should explain the pale cyanotic expression of asthmatic people, and also explain the increased activity of the respiratory muscles. This theory, which is supported only by the fact that nitrite of amyl, with

* Riegel og Edinger, Experimentelle Untersuchungen zur Lehre vom Asthma, Zeitsch. f. klin. Medicin, V. B. s. 413, ref. bg Schmidtborn; see also Holm, Inspiratorisk Dyspnoe-Forhdl. i det norske medis. Selskab., 1888, p. 83,Norsk Magaz. f. Læger, Juni,

+ H. Schmidtborn, Ueber Asthma nervosum, Volkmann's klin. Vortr., Nr. 328, 1889.

its power to paralyse the vessels, acts favourably on asthma, is very uncertain and hypothetic.

As will be seen by the preceding review of the different theories on Asthma which have appeared in the course of time, it is very difficult to gain a firm position in this question as the different theories stand in distinct opposition to one another. Sée's opinion is certainly the most plausible, especially as he accentuates the central seat of the affection in the medulla oblongata as the essential thing, and because he considers the complaint to be a neurosis caused by an increased reflex irritability of the centres of the medulla oblongata. This only makes it possible to explain the incongruity offered by the different clinical features of Asthma, and it gives, both in pathological and anatomical as well as in clinical and therapeutic respects, the key to many problems, the solution of which was impossible under the old supposition that Asthma was the result of a peripheric (lung or vagus) affection. From this point of view it was formerly impossible to give a satisfactory explanation of all the symptoms, and therefore a number of hypotheses were set up which only served to make the comprehension of the real nature of Asthma quite impossible. Several authors such as John N. Mackenzie have certainly maintained the necessity of taking the increased irritability of the central nervous organs sideration as necessary for the comprehension of the state of many asthmatic patients, but it has nowhere been so clearly expressed as by Sée, and no one before him has, with this as starting point, given so clear and precise a description of the nature of Asthma.

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It is not the intention of this essay to consider all the different forms of nervous asthma, but to speak only of reflex asthma, and specially that form of reflex asthma that originates in the

nose.

The reflex or eccentric nervous asthma is, in comparison with the central asthma (Bamberger),* by far the most frequent. Riegel distinguishes between the direct and reflex asthma.

The direct, and specially the central form is very rare. Saltert mentions in his work two cases that might be considered as central asthma. The one case was of a child of 10, who during an acute hydrocephalus had several typical asthmatic attacks; the other case was a man, aged 50, who suffered from epilepsy, and the epileptic attacks alternated with attacks of asthma. Biermers thinks that in some cases asthma is caused by a pressure of the swollen tracheo-bronchial glands on the vagus nerve. Taken from Sée's point of view these cases must be interpreted as reflex asthma, as the irritation of the vagus passes indirectly (through the medulla oblongata) to the respiratory muscles.

The indirect reflex asthma, on the contrary, is far more frequent, and has been known since the time of Willis. In the introduction to this essay I have mentioned several examples of this, and towards the end of the last century Darwin stated that asthma can originate from every possible part of the human body. It was meanwhile only the abdominal organs that were taken into consideration, and it was specially the digestive disorders against which the older therapeutists directed their causal treatment in cases of asthma. The diet played a great, very often the only part in the treatment at that time (see Salter). S It was only after Voltolini had published his experiences of the dependence of asthma upon the nose in many cases, that attention was first called to this point.

* Bamberger, loc. cit., p. 109.
Salter, loc. cit., pp. 43-44.
I Biermer, loc. cit., p. 55.
§ Salter, loc. cit., p. 43.

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