February 17, 1888.] 



SCIENCE. 



To my mind, the only one adequate is to be sought in physiological 

 reversion. Whether there are not examples of it even when the 

 nervous system is intact, as in excessive action of the bladder, 

 ureter, etc., in cases of obstruction, is worthy of consideration. 



Dr. Pye-Smith {Jourtial of Physiology, vol. viii.) has maintained, 

 from certain experiments made by him, that the vessels of the ear 

 of the rabbit, etc., do not regain their tone after section of the 

 nerves concerned, and concludes that nerves are not essential to 

 nutrition. However it may be as to the first proposition, I cannot 

 help thinking that the author's conclusions are broad to the verge 

 of decided error when applied beyond the case in point. 



Assuming, however, that in most instances the vessels do not 

 regain tone, I should interpret the case as one of still more remote 

 reversion to a condition when nerves were not required for nutri- 

 tion, — a condition existing in several large groups of animals. 

 Such a case in the mammal must be very rare, however, and is 

 offset by thousands of facts that show that nutrition is dependent 

 on nervous connection. It would appear that oxygen may be ab- 

 sorbed both from the skin and the alimentary canal ; and, if we may 

 judge by many analogous instances, this capacity would be aug- 

 mented when the individual greatly needed such help, owing to 

 imperfect action of the lungs. In such instances we have, on the 

 one hand, a retained function operating in man to a very minor 

 degree; but, as is now well known, in batrachians the skin is an 

 important respiratory organ, though also one acting very much 

 in a manner supplementary to the lungs, as circumstances neces- 

 sitate. When in man the skin and alimentary canal function as re- 

 spiratory organs to an unusual degree, we have physiological or 

 pathological reversion. 



It is well known that in certain pathological conditions (hysteria, 

 etc.) large quantities of gas are secreted by the alimentary tract; 

 nor is this so surprising when it is remembered that the digestive 

 canal and the respiratory organs have a common origin from the 

 same cell layers of the embryo. 



If our swallowed oxygen can be absorbed by the alimentary 

 canal, of which there is no reasonable doubt, it is plain that we re- 

 tain a function discharged by an analogous organ, the air-bladder 

 of fishes.' Certain groups of turtles (if not all, occasionally, as I be- 

 lieve) have a species of pharyngeal respiration. Oxygen is ab- 

 sorbed from the water gulped into the pharynx, and possibly the 

 case of absorption of gases from the alimentary canal of mammals 

 is still more like this than the analogous instances already men- 

 tioned ; but, at all events, there is a potential capacity in the ali- 

 mentary tract of man for respiratory functions which is unquestion- 

 ably under certain circumstances considerably developed ; and the 

 most natural explanation is physiological reversion. 



In an allied system, the renal, we have evidences of physiological 

 reversion. In most fevers the skin is less active, and the kidneys 

 function excessively or at least differently ; the urine, though scanty 

 in quantity, is of high specific gravity, and thus resembles more the 

 same secretion in not only lower mammals, but the lower divisions 

 of vertebrates. In a whole host of diseases " there is a great in- 

 crease of a constituent which is but scantily present in normal 

 urine, — uric acid. But uric acid replaces urea in fishes, reptiles, 

 and birds; and in not a few cases in man in which the uric acid is 

 increased the urea secretion is diminished. That man's kidneys 

 should thus have the capacity to function in a manner analogous 

 to those of lower forms, calls for explanation. The fact that in 

 such cases the reversion does not wholly cover the functional dis- 

 turbance arising from or giving rise to this change, is not a seri- 

 ous objection ; for it is not to be supposed that an animal adapted 

 to new conditions should, by any reversion to an ancestral state, 

 escape wholly, or even in great part, the penalties of incomplete 

 adaptation. 



In the digestive system of man and other mammals we have in- 

 teresting instances of physiological and pathological reversion. Re- 

 g'urgitation of food is normal in some birds, and I am inclined to be- 

 lieve that it is more common in lower vertebrates than has been as yet 

 clearly ascertained. But the remarkable regurgitation of ruminants 

 seems to be a specially developed function. Different groups of 



^ See a paper by Gage in the Proceedings of the American Association, vol. xxxiv. 

 ^ The writer discussed the subject of uric acid in a short paper in the Medical 

 Neius for June 27, 1885. 



animals vomit with very varying degrees of facility. There is to 

 my own knowledge in man a tendency to antiperistalsis in the 

 oesophagus, if not the pharynx, independent of acid eructations. 

 Some individuals experience this when there is interference with 

 the regularity of the action of the bowels. Cases have been re- 

 ported in which there seemed to be habitual regurgitation of food, 

 like that of birds or even ruminants. Here again the most natural 

 explanation seems to be that the alimentary canal of mammals, in- 

 cluding man, retains a capacity to revert to a condition existing in 

 a higher degree in antecedent forms ; or, to interpret the matter 

 slightly otherwise, that man retains a capacity which in some lower 

 forms has been specially developed (ruminants, etc.), and which in 

 himself, under certain abnormal circumstances, becomes greatly 

 developed, — -facts explicable by general community of descent. 



In the cases in man referred to above, the mere law of habit 

 does not of itself suffice to explain the facts : indeed, apart from 

 the wider laws of descent, there is very little basis for the action of 

 such a principle ; there is no fulcrum for the lever, or, at best, a 

 very unsteady one. 



In diseases of the blood or blood-forming organs we have some 

 remarkable instances of functional reversion. Though exact 

 quantitative determinations of hsemoglobin are wanting for most 

 lower vertebrates, there can be do doubt that in mammals the quan- 

 tity of this substance furnished to the system within a given time is 

 much greater than in those groups requiring less oxygen for their 

 tissues, in conse quence of a feebler cell activity. But in cases of 

 anasmia in man the quantity of hamoglobin may be greatly dimin- 

 ished, one result of which is that the subject is reduced not only as 

 regards the condition of the blood, but in several other respects, to 

 a state bearing a more or less close resemblance to life in the lower 

 vertebrates. There is diminished activity in the locomotor, the 

 nervous, and other systems of the body. The subject requires rest, 

 careful feeding, quiet of the mind, etc. The treatment is uncon- 

 sciously based on this fact of reversion. It may be stated, in truth, 

 that the ansmic subject is unable to discharge the functions which 

 are most characteristic of man, and that he naturally deports him- 

 self like a lower form. In leukEemia there is a still more marked 

 reversion, for the blood in this disease approaches the condition 

 found in the invertebrates, in which, as a rule, the red blood cell 

 or haemoglobin in any form is wanting. This being the case, it is 

 not surprising that the disturbance of the normal functions is so 

 great : the marvel is rather at man's capacity to adapt at all to such 

 unnatural conditions ; which, however, is clearer on the doctrine of 

 descent from lower forms and in the light of the conception of 

 physiological reversion than by any other explanation. 



In that form of anaemia or chlorosis due to an imperfectly de- 

 veloped vasculai system generally, we surely have a clear instance 

 of reversion, so marked that during the whole lifetime of the indi- 

 vidual there may never be other than the most defective adaptation 

 to environment. 



Instances of cyanosis due to permanence of foetal conditions of 

 the circulation, and therefore resembling those normal to the frog 

 and turtle, are such clear cases of human reversion as only to re- 

 quire mention. 



In cases of valvular diseases with dilatation of the heart, or in- 

 deed any condition of this organ that permits of regurgitation with 

 imperfectly aerated blood, we have similarly a reversion. It will be 

 found that in not a few diseases of the heart, — in the condition of 

 that organ during fainting ; after shocks which have temporarily 

 suspended many functions of the nervous system, and in conse- 

 quence greatly imperilled life, — in all such cases it will be found 

 that those parts of the heart the earliest developed in the history of 

 the animal series are the very parts to continue their action latest. 

 Now, this is at once fortunate for the mammal, and of great sig- 

 nificance, inasmuch as the latest investigations show in the 

 clearest way that the action of the ventricles is dependent on the 

 functional integrity of the sinus and auricles, especially of the sinus. 

 Suppose that the reverse were the case, and the sinus (or great 

 veins) and auricles were the first to cease pulsating : the beat of 

 the ventricle would be of comparatively little use ; but apart from 

 this, what explanation can be given of this peculiar sequence in the 

 mammal independently of derivation from lower forms, which 

 makes all clear ? If this doctrine of physiological reversion went 



