452 Dr. W. Marcet on the Nutrition of 



sence of the water, which acts a part not unlike that it would 

 take in the formation of a jelly. 



In consumption it appears that the proportion of water in every 

 ilesh -molecule the blood yields is too high, and moreover that the 

 constituents of these molecules are not bound together by water 

 as they should be ; at the same time the chloride of sodium of the 

 blood begins to diffuse into the tissues by a physical process 

 which had been kept in abeyance during the maintenance of 

 health, passing through the capillary vessels into the flesh, just 

 as it would have done through the diaphragm of a dialyzer into 

 water; hence it is that in consumption, the physical force of 

 matter is gradually overcoming that force which belongs exclu- 

 sively to life, the nature of which is still a mystery; and the slow 

 ebb of life in phthisis is a gradual return to a purely physical 

 condition. 



On Pulmonary Tissue and its Nutrition in Phthisis. 



My inquiries into the chemical changes pulmonary tissue un- 

 dergoes in phthisis has led to some very interesting results. 



In health the lungs consist of a tissue, which, from its struc- 

 ture, allows readily of expansion and contraction; this tissue 

 becomes thoroughly permeated with air during respiration, the 

 oxygen of which diffuses through the substance of the lungs 

 and the pulmonary capillary vessels into the blood, the carbonic 

 acid being eliminated from the blood by a similar process. This 

 gaseous diffusion can only take place so long as the soft and deli- 

 cate walls of the capillary vessels and pulmonary air-vesicles 

 remain physically unaltered; if they should become hardened 

 or changed in any other way, the diffusion of the gases through 

 their substance must be interfered with or entirely checked. 

 Now in the most common form of phthisis, as shown by Dr. 

 Sanderson, the process begins by a new growth of the inter- 

 stitial tissue of the pulmonary honeycomb, having its seat in 

 the very walls of the blood-vessel. Even at an early stage, 

 the effect of this is not only to diminish the circulation of blood 

 in the affected part, but to render the pulmonary capillaries 

 more and more unfit for the exchange of gases, by diffusion, 

 between the blood and the inspired air. Eventually the air- 

 cells or alveoli in their turn become filled up with a solid ma- 

 terial, losing completely their fitness for respiration. Then the 

 tissue softens and breaks down, apparently from the loss of the 

 colloid state of the consolidated pulmonary tissue. It is this 

 last stage which is usually observed after death ; and the pulmo- 

 nary tissue T have submitted to analysis was mostly in that con- 

 dition. The method of analysis I adopted was precisely the 

 same as that which had been applied to flesh and healthy pul- 

 monary tissue. 



