PHYSIOLOGY. 



653 



Cases of poisoning by food of a relatively in- 

 nocuous character are not uncommon. Some 

 portion of the ingesta becomes un irritant 

 |H>isn, a fit of indigestion ensues, and often 

 tlir offending substance is speedily expelled ly 

 vomiting. Idiosyncrasies play a part here; it is 

 known that certain articles of diet, such as 

 cheese and shell fish, are toxic to seme persons. 

 (Jen. Tally the state of the alimentary canal at 

 the time is responsible. The most common and 

 best known of the various forms of indigestion 

 is that in which, from the absence or the de- 

 ficiency of gastric juice and other digestive 

 fluids, the alimentary bolus becomes a gastro- 

 intestinal irritant, provoking vomiting, purging, 

 and a catarrhal condition of the digestive tract. 

 A second stage in the process of acute indiges- 

 tion arises from the presence of abnormal fermen- 

 tations and decompositions in the alimentary 

 canal. The food substances, under the influence 

 of bacteria unrestrained by the antiseptic di- 

 gestive fluids, break up into organic acids and 

 alkaloidal products of a lower order, which are 

 in part absorbed and produce constitutional 

 disturbances. This stage borders very closely on 

 that of ptomaine formation. There is good 

 reason to regard cholera nostras and the gastro- 

 intestinal catarrh of infants as kinds of ptomaine 

 poisoning due to multiple causes, of which 

 weakening of the alimentary canal and conse- 

 quent poverty of digestive fluids, the ingestion 

 of food of an indigestible character, the putre- 

 factive decomposition of the latter under the in- 

 fluence of microbes, and the formation of toxines, 

 are the principal factors. 



Miscellaneous. The remarkable absence of 

 parasitic growths on the carapaces of crustaceans 

 has struck B. W. Hardy as a notable fact ; and 

 the more so as there appears to be no mechan- 

 ism obviously able to produce this cleanliness. 

 Every animal that inhabits the water, or has a 

 habitually moist external skin, is liable to have 

 larvae and spores continually settling on its sur- 

 face to develop into embarrassing growths, un- 

 less some method of removing or destroying 

 them is present. In many animals the way in 

 which the surface is kept clean is partly obvious. 

 Commensal forms feeding on matter adherent 

 to the skin contribute to the result. The period- 

 ical shedding of an external cuticle is a radical 

 means of ridding the animal of growths that 

 may have obtained a hold in spite of other pre- 

 ventive devices, and the continuous desquama- 

 tion which is characteristic of the stratified epi- 

 thelium of the higher vertebrates is a more 

 subtle device of the same nature. The append- 

 ages of some animals are used for removing the 

 larger forms of adherent bodies. In the mam- 

 malia multitudes of phagocytic wander cells are 

 poured on to the surface to "ingest foreign parti- 

 cles. Rubbing and scratching the body are of 

 great service in removing foreign matters. The 

 conspicuous cleanliness of crustaceans is not ac- 

 counted for by any of these provisions. Even 

 the periodical shedding of their cells is not suf- 

 ficient, for that does not occur often enough to 

 prevent the growth of parasites. Mr. Hardy's 

 investigations lead him to the conclusion that 

 the source of protection is to be found in the 

 action of the surface slime of animals and of 

 phagocytes. The surface slime may have a me- 



chanical action ; for the author thinks it may 

 be taken for granted that the presence of a film 

 of soluble slime on the surface of an animal im- 

 mersed in water would, like the copper sheath- 

 ing of ships, mechanically prevent the occur- 

 rence of parasitic growths by continually form- 

 ing a fresh surface ; or the slime may have a 

 specific poisonous power directed mainly per- 

 haps against the more minute and subtle forms 

 of vegetable parasites. It has been observed 

 that exposure to the poisons produced by an- 

 thrax causes an increased elimination of a rose- 

 staining substance on to the external surface 

 and into the blood plasma, and Hankin has 

 shown that the blood serum of animals contains 

 a substance which has a bactericidal action, and 

 to which the name alexine has been applied. 

 This alexine, he believes, has its origin in the 

 blood corpuscles. Fresh force is thus given to 

 the conception of Hanvier, who long ago styled 

 the wander cells unicellular glands. Possibly the 

 rose-reacting substance of Daphnia has a specific 

 bactericidal action, and contains an alexine. It 

 is always produced in increased quantities when 

 the animal is infected with pathogenic growths, 

 and it can not be regarded as the product of the 

 microbes in or on the bodv of the animal. 



The preference shown by tuberculosis for the 

 apices of the lungs has been often explained by 

 the assumption that the apex is not participating 

 fully in the respiratory movements, and that 

 the diminished ventilation of that locality is the 

 cause of its predisposition for the disease. But 

 under the theory that an invasion of tubercle 

 bacilli into the lungs is at the bottom of the dis- 

 ease, we should rather expect that if the apex 

 breathes less the bacilli will have fewer chances 

 of getting in there, and in consequence this part 

 of the lungs, instead of being predisposed for the 

 disease, should rather show a certain immunity 

 against it. To meet this argument, A. Hanau as- 

 sumed that the expiration is indeed less, whereas, 

 the inspiration is rather better in the apex than 

 in the other parts of the lungs, and that there- 

 fore all corpuscular elements of microscopical 

 dimensions, like the bacilli, dust, etc., have a 

 greater chance to get in the alveoli of the apex, 

 while their chances to get out of them by the 

 expiration is reduced. This hypothesis would 

 indeed cover the pathological phenomenon satis- 

 factorily, if it were not that the normal breath- 

 ing also has to be taken into consideration. 

 Physiology can not afford to ignore this prob- 

 lem, or to solve it with mere theoretical specu- 

 lations. As it is very difficult to find an exact 

 method of ascertaining directly the degree of 

 distentions of the apex, as compared with those 

 of other parts of the Jungs during normal 

 breathing, Dr. S. J. Meltzer first turned his at- 

 tention to the steadily attending phenomenon of 

 the change of the intrathoracic pressure coin- 

 cident with the inspiration and expiration. The 

 purpose of his investigation was to infer the 

 amount of respiration in different localities from 

 the accompanying changes in the intrathoracic 

 pressure. It was found, from his experiments on 

 the mediastinum, to be probable that the apices 

 and the back part of the upper third of the 

 lungs do not participate in the breathing so 

 largely as the other parts of the lungs do; yet, 

 in consideration of the importance of this con- 



