Wednesday, September 7, 2016

1842: Longet's proves nervous theory of asthma

William Longett (1811-1871)
In 1808 Dr. Franz Reisseissen discovered muscular fibers wrap around the air passages in the lungs, and in 1840 Dr. Charles Williams proved these fibers spasm in the presence of certain stimuli.  Yet there remained one missing link necessary to prove the spasmotic and nervous theories of asthma.  The man up to the task was Dr. Francois Achille Longet of France. 

Longet did a variety of experiments on the anotomic nervous system, which is a system of nervous system that controls involuntary action, such as the beating of your heart, your rate of breathing, digestion, sexual arousal, dilation and contraction of the pupils, salivation, etc. In other words, it controls all the actions of the body that a person does not control (the brain controls them). 

In 1840 he must have heard of the experiments of Williams, so it was only a few years later, in 1842, that he aimed to see if he could find the missing link between the brain and the lungs to prove that the brain, or the nervous system, was responsible for asthma.  

Dr. J.B. Berkart, in his 1878 book "On Asthma," explains: 
Yet one link was wanted to complete the chain of evidence in favour of a bronchial spasm. As yet nothing was known of the innervation of the bronchi. Irritation (galvanization) of the vagus (pneumogastric) had produced no effect upon their calibres, and Dr. Williams was therefore led to conclude that "the muscular fibres seem not to be excitable through the nerves of the lungs".
Soon, however, Longet not only confirmed in the main the results obtained by Williams, but added that in his experiments irritation of the pneumogastric nerve always produced spasmodic contraction of the bronchi, whereas section of the nerve led to emphysema. Of the bronchial stricture he could satisfy himself by watching with a magnifying glass, but as to the occurrence of a similar process in the pulmonary tissue he had no means of judging. Still, he believed that such took place, although the presence of muscular fibres in the air-vesicles was then as doubtful as it is to-day. For, since section of the vagus causes emphysema, i.e., distension of the air vesicles, there must be muscular fibres which, if liable to paralysis, are liable also to spasm. (1, pages 26-27)
Now, just for the record here, the vagus nerve is a main nerve that runs down from the brain and supplies the heart, lungs and the various organs of the body. Longet proved irritation of this nerve would cause bronchospasm.

However, Berkart said that some of Longet's experiments, along with those of others, often led to incorrect speculations.  He said:
It cannot fail to be observed that those hasty applications of the results of the experiment to the pathology of asthma led here, as they always do, to unwarrantable conclusions. If, indeed, Longet were correct in this, that bronchial stricture and emphysema are due the one to a plus, the other to a minus state of irritability of the vagus, it would necessarily follow that, as asthma and emphysema are almost always associated, spasm and paralysis of the self-same muscles could co-exist at the same time, each independently of the other, manifesting itself in its own peculiar way. Such deduction necessarily follows from the premisses. (1, pages 28-29)
Regardless, while Williams proved irritation of the muscular fibers in the lungs may cause bronchospasm, Longet proved irritation of the vagus could cause bronchospasm. Thus, for the rest of the century various authors referred to the experiments of Williams and Longet as proving both the spasmotic and nervous theories of asthma.

The experiments of Williams and Longet were later verified by other physicians, including Moritz Heinrich Romberg, Alfred Wilhelm Volkman, Traube, Bernard, and Bert.  They all proved that irritation of the vagus caused "contractions of the air tubes."  (3, pages 5-6)

Based on this evidence, most authors on the subject of asthma believed in the nervous and spasmotic theories of asthma, citing Reisseissen, Williams, Longet and Volkman as promulgators of the evidence.

  1. Berkart, J.B., "On Asthma: It's Pathology and Treatment," 1878, London, J. & A. Churchill
  2. Brown, Orville Harry, "Asthma, presenting an exposition of nonpassive expiration theory," 1917, St. Louis, C.V. Mosby Company
  3. Thorowgood, John Charles, "Notes on Asthma: It's Nature, Forms, and Treatment," 1878, London, J. & A. Churchill
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