May 26, 1904] 



NATURE 



specific gravity after meals, the rise reaching its maximum 

 point (e.g. from 106 1 to 1065) in an hour. The specific 

 gravity then begins to fall, settling down to the initial 

 point at the conclusion of the wave-like disturbance 

 (Fig. 2, k). On the other hand, the blood derived from the 

 finger uncompressed affords a specific gravity which follows 

 the contrary course, that is to say, it falls and then rises 

 (big. 2, b). When the digestive disturbance is over, the 

 variations in the blood, like those in the circulation, 

 cease, and the readings in normal subjects at rest continue 

 to be alike in both samples (before and after compression) 

 until the following meal. 



The digestive exudation of tissue lymph. — On reviewing 

 the foregoing data it is obvious that they indicate strictly 

 concurrent events. .\11 the four series of variations follow 

 exactly the same curve. What is the link which binds them 

 together? If we suppose that the ingestion of food in some 

 way raises the capillary blood pressure which exudes a 

 filtrate of a portion of the liquor sanguinis into the areolar 

 spaces, all the changes in the blood which I have described 

 will naturally follow (see Fig. 2). In proportion to the 

 exudation under a rising capillary blood pressure, the blood 

 will become more and more concentrated in chromocytes 

 and in hcemoglobin, and inasmuch as its specific gravity 

 mainly depends on the corpuscles, the density of the blood 

 will rise pari passu with the increased concentration. Then, 

 when the capillary pressure begins to fall, as it does after 

 the acme of the digestive disturbance has been attained, the 

 concentration of the blood diminishes, and we may assume 

 that either absorption of the watery elements of the effused 

 lymph overbalances exudation or that the effusion is being 

 returned by the lymphatics to the blood. Now I have shown 

 that none of these alterations in the blood could have been 

 ascertained by the examination of blood derived from the 

 finger in the ordinary way ; they only become apparent after 

 the compression of the tissues by the rubber rings, which 

 removes the extra-capillary fluid and enable us to obtain the 

 blood undiluted by that fluid. But the progressive readings 

 of the ordinary samples of blood, though valueless, and 

 actually misleading when accepted as independent testimony 

 of blood changes during digestion, become instructive when 

 compared with the readings of samples obtained after com- 

 pression, for they then afford a measure of the amount of 

 fluid withdrawn from the blood. The differential readings 

 of the ha?mocytometer tubes made every fifteen minutes after 

 a meal show the greatest divergence, and therefore the 

 largest quantity of tissue fluid, just at the time (an hour 

 after a meal) when the digestive blood pressure wave and 

 the concentration of the blood attain their maximum de- 

 velopment. The difference, indicated by the scale on the 

 tubes, will amount to from 15 to 20 per cent. ; it will then 

 gradually diminish, and will finally disappear in from two 

 and a half to three and a half hours, and will not reappear 

 until after the next meal or until exercise is taken. The 

 amplitude and duration of the lymph wave are influenced 

 by various conditions, such as the tone of the subject, the 

 bulk and nature of the meal, the use of beverages, rest, or 

 exercise. 



Other rhythmical digestive variations. — I will now direct 

 your attention to other physiological variations produced by 

 the ingestion of food, synchronous with the foregoing. 

 These are : — (i) the digestive curve of augmented respir- 

 atory exchange determined by Fredericq and other 

 observers ; (2) the gastric juice curve of Pawlow ; and (3) a 

 digestive rhythmical variation of muscular contractility, 

 which came to light while studying the effects of muscular 

 tension on the arterial pressure. It was found that when 

 tissue-lymph was not apparent (e.g. before meals), the 

 tension raised the arterial pressure to a maximum degree 

 (e.g. 40 mm.), whereas when the lymph was fully effused 

 (an hour after a meal) the pressure could only be slightly 

 raised (5 or 10 mm.). The digestive curve of muscular 

 contractibility (i.e. the capability of being contracted) is 

 therefore the reverse of the lymph curve, and it is inferred 

 that the e.xudation of the lymph into the muscular tissue 

 checks I he shortening of the muscular fibres, and thus 

 diminishes the effect of their contraction on the intra- 

 muscular vessels. 



These observations on the condition of the muscles during 

 digestion, therefore, confirm the teaching as to the outflow 

 and absorption of lymph furnished by the differential ex- 



NO. 1804, VOL. 70] 



amination of the blood. At the termination of the digestive 

 disturbance there is apparent a gain in the contractile 

 energy, as expressed in an additional rise of the arterial 

 pressure produced by muscular tension. This gain (which 

 only becomes evident after the absorption of the lymph) 

 varies from 5 to 20 millimetres, according to the nature 

 of the food consumed and the need for recuperation. 



The effects of typical meals on the digestive lymph ftoiv. — 

 Let us now study the digestive curves of lymph exudation 

 produced by four different kinds of meals. First, the 

 ordinary mi.xed meal containing the usual proportions of 

 animal food, vegetables, and farinacea ; secondly, the meat 

 meal, consisting of animal food in various forms, with 

 chcp^ie and butter and a very little toast ; thirdly, the vege- 

 table n-enl, with farinaceous puddings, fruit, and cheese ; 

 and fourthlv, the milk meal, milk, bread, and farinaceous 

 puddings. In each case the fluid supplied was a tumbler of 

 water, and the amount of food was merely limited by a 

 feeling of satisfaction. Sugar and salt (two grams of 

 each) were taken in the same quantity at all the solid meals. 

 The meal was at one o'clock, and the same subject was 

 throughout submitted to observation. No exercise was 

 permitted for an hour before and after meals, nor until 

 the digestive disturbance had quite subsided. Observations 

 were made just before the meals and every fifteen minutes 

 after them. The results are epitomised in the following 

 table (Table L) :— 



Table I. 



Lympli effusion 

 The meal 



Roast meat ... 



Mixed 



Vegetable 



Milk 7-5 14 



You see that the lymph curves produced by these several 

 kinds of meals vary enormously in amplitude and length, 

 and in the following descending order : — meat meal, 

 ordinary meal, vegetable meal, and milk meal. The net 

 gain in muscle contractility shown by the tension test aftei 

 the subsidence of the digestive disturbance and the removal 

 of the lymph is in the same order, expressed by the follow- 

 ing figures : — 15 (meat meal), 10 (ordinary meal), 7 (vege- 

 table meal), and 3 (milk meal). Some light will be thrown 

 on these results by studying the effect of the separate food 

 elements. 



The effect of the food elements on the production of tissue 

 lymph. — I will first mention those substances which, accord- 

 ing to my observation, do not alter the blood pressure or 

 cause the flow of tissue lymph : — cold water, starch, fats, 

 gelatin, proteid as represented by myosin or egg-albumin, 

 the sugars (cane sugar, glucose, maltose, galactose, 

 mannose, dextrose, and inulin), pepsin, and hydrochloric 

 acid. Cold water (e.g. 500 cubic centimetres, or a little 

 more than 16 ounces) has no effect, but the same amount 

 of warm water lowers the arterial pressure. This is there- 

 fore a temperature effect. In regard to proteids, I selected 

 chemically pure myosin (muscle proteid) and white of egg 

 as representative of the group. So far their effects have 

 been negative. In support of this conclusion we have also 

 the fact that the lymph exudation produced by a meal of 

 roast beef is 30 per cent., whereas that caused by a meal 

 of boiled meat is only 7 per cent. All the sugars named also 

 produce negative results. There are, however, other sugars 

 (glvcogen, lasvulose, and lichenin) which have been found 

 decisively to affect the blood pressure and the flow of lymph. 



Inorganic salts. — I will here only refer to sodium and 

 potassium chlorides, as my observations on the effects of 

 other salts are not sufficiently advanced for publication. 

 Sodium chloride, in percentages varying from 15 to 2.0, in- 

 variably raises the arterial pressure and increases the outflow 

 of tissue lymph ; four grams produce in thirty minutes 

 the exudation of 15 per cent, lymph, which is completely 

 absorbed in thirty minutes more. Potassium chloride 

 lowers the arterial pressure, four grams producing a fall 

 of from 10 to 12 millimetres of mercury. Sodium chloride 

 increases and potassium chloride diminishes the digestive 

 curves. When these two salts are taken in equal propor- 

 tions — e.g. tv.'O grams of each — their effects on the blood 

 pressure and lymph flow neutralise each other. 



