Uniformity in the percentages of carbon dioxid was immediate in the fifth experiment and continued for more than one and a half hours. During this period five samples were analyzed. The average was 5.61 while 5.53 and 5.64 were the figures showing the greatest deviation. from the mean.

Again, in the sixth experiment the carbon dioxid exhibited uniform behavior with a period of preliminary fluctuation. The period of observation covered one and a half hours and during this time six determinations were made with an average of 5.42, the highest and lowest percentages being respectively 5.66 and 5.20. The respirations in this animal were quite irregular in depth.

In the last experiment three determinations in the first half hour fluctuated; these, however, were followed by a period of uniformity lasting two hours during which six samples were obtained averaging 5.49, with a minimum percentage of 5.42 and a maximum of 5.56.

There was no persistent upward or downward tendency in the percentages of any one experiment. In nearly all cases the last percentage of the period of uniformity was identical with the first percentage of the period. This is rather interesting in view of the steady fall in the body temperature. A fall in body temperature seemed rather to occasion a fall in the percentages of carbon dioxid in Scott's (14) experiments.

I am unable to state definitely the cause of the preliminary fluctuations sometimes observed. It is significant however that in all those experiments in which analyses were not begun until 12.00 m. or later this phenomenon did not appear, except in the experiment of March 7 in which the breathing in the beginning was of the periodic type.

Chloretone was always given between 9.30 and 10.00. It is possible that the volatile nature of this substance may have interfered with the analysis of the air.'

The method is clearly capable of a variety of modifications and ought to be useful in the solution of a number of problems bearing on the physiology of the respiration. The percentages in the above experiments are not absolute values and hence the results of one animal must not be compared with the results obtained in another animal. This is partly to be accounted for by the fact that the negative pressures were not the same in the different dogs; in some more air was allowed to remain in the pleural sacs than in others. Neverthless it is evident that the percentages of carbon dioxid in samples obtained by this method may exhibit uniformity for periods as long as three and one-half hours and that the variations are no greater than one obtains by the use of other methods.

BIBLIOGRAPHY

(1) WOLFFBERG: Pflüger's Arch., 1871, iv, 467.

(2) NUSSBAUM: Arch. f. d. gesammt. Physiol., 1873, vii, 296.

(3) LOEWY AND VON SCHRÖTTER: Zeitschr. f. exper. Path. u. Therap., 1905, i, 258. (4) PLESCH: Zeitschr. f. exper. Path. u. Therap., 1909, vi, 487.

(5) PORGES, LEIMDÖRFER, MARKOVICI: Zeitschr. f. klin. Med., 1911, lxxiii, 395. (6) HALDANE AND PRIESTLEY: Journ. Physiol., 1905, xxxii, 228.

(7) BOYCOTT AND HALDANE: Journ. Physiol., 1908, xxxvii, 358.

(8) FITZGERALD AND HALDANE: Journ. Physiol., 1905, xxxii, 487.

((9) LINDHARD: Journ. Physiol., 1911, xlii, 344.

(10) BOOTHBY AND PEABODY: Arch. Int. Med., 1914, xiii, 503.

(11) SCOTT: Journ. Physiol., 1908, xxxvii, 314.

(12) MELTZER: This Journal. (See foregoing article.)

((13) HALDANE: Methods of air analysis, 1912.

(14) SCOTT: Journ. Physiol., 1908, xxxvii, 314.

* Among other factors that may play a rôle is the possible alteration in the volume of the dead space.

THE VISCOSITY OF LYMPH

R. BURTON-OPITZ AND R. NEMSER

From the Physiological Laboratory of Columbia University, at the College of Physicians and Surgeons, New York

Received for publication October 9, 1917

As the method which has been made use of by Burton-Opitz (1) in determining the viscosity of different body-fluids has been described in an earlier paper, it need only be mentioned at this time that the experiments now under discussion purpose to ascertain the factors required to calculate the coefficient of the viscosity of lymph. The apparatus is arranged in such a way that it is possible to measure how large a quantity of this fluid escapes through a capillary tube of known length and diameter in a given period of time and under a certain pressure. The coefficient derived from these factors is then compared with the coefficient for distilled water at 37°C. which, in accordance with Poiseuille (2) equals the value 4700.

The present experiments were performed upon dogs which had received a moderate amount of fatty meat about four hours previously. Light ether narcosis was employed. The lymph was gathered from the central orifice of the thoracic duct. It became necessary at times to hasten its flow by exerting gentle pressure upon the abdominal wall, because as lymph clots very rapidly, its passage through the viscosimeter could not be permitted to consume a longer time than about one minute. From 2 to 3 cc. of lymph were used for each determination. The specific gravity was ascertained with the help of small pycnometers possessing a capacity of about 4 cc.

The results of these determinations are compiled in table 1. It will be seen from this that the viscosity of lymph varies considerably. The coefficients here recorded lie between the figures 2406 and 3029 and present the average value 2682.5. If this coefficient is compared with the coefficient for distilled water of 37°C., it will be found that lymph possesses a viscosity which is 1.7 greater than that of water. It must be emphasized, however, that these determinations have been made during the absorption of fat and that, therefore, these values are some

what above those obtainable with perfectly clear lymph. The nearest approach to the watery type of lymph was yielded by dog 5, this experiment having been performed almost six hours after the ingestion of food. The relatively high numerical value of this coefficient (3029)

indicates that this lymph possesses a viscosity only 1.5 times greater than that of distilled water of 37°C.

In a similar way, it may be gathered that increasing absorption heightens the viscous resistance of the lymph. Thus, the coefficient 2406 obtained by experiment 8 shows that this lymph is almost 2.0

times more viscous than distilled water of 37°C. In this connection, brief reference might be made to the fact that the viscosity of blood is almost 5 times greater than that of distilled water (3) while that of ox bile (4) is only 1.8 and that of saliva only 1.4 times greater (5).

The specific gravity follows a course parallel to that of the viscosity. The values recorded above vary between 1.0119 and 1.0230. The average value is 1.0165. The coagulation-time which was determined by the method of inversion of a small test tube filled with a small quantity of fresh lymph, varied between one and seven minutes. The average time was two minutes and a half. It is evident, therefore, that

viscosity experiments upon lymph necessitate the same precautionary measures as those made upon the circulating blood. The time required for the completion of each test should not be longer than one minute. Table 2 is intended to illustrate the changes which the lymph of the thoracic duct undergoes in consequence of the stimulation of the greater splanchnic nerve. The experiments with which we are concerned at this time, are those designated in table 1 as 6 and 7. In both cases the left greater splanchnic nerve was used, shielded electrodes having been applied to it through a small opening in the abdominal wall. Having collected a sufficient quantity of lymph for the determination of the normal viscosity and specific gravity, the two subsequent collections were made while the aforesaid nerve was being stimulated with a tetanic current of medium strength.