Copenhagen,
March 25, 1931Dear Dr. Drinker,
At intervals ever since your Christmas letters came to Professor Krogh and to me we have been wondering what you were doing and how the lymph experiments were done. It is a shock to Professor Krogh to have so much lymph running around - but he has had other shocks this year. He believes that Dr. Landis' experiments on the capillary pressure really are so - but yet it is hard for him to think the capillary pressure in general is higher than he had thought it - perhaps yet other capillaries are different, though a good many have been measured now. So it may be with lymph flow!
I'm putting in a little sheet to tell you in brief what we have been working most of the year on. It is - as I guess I wrote you earlier - the relation of the pressure put on the veins to the filtration observed by a plethysmograph, with variations in position, measurements of colloid osmotic pressure of serum and so on. There have been certain difficulties, but gradually we have fixed ways around them until we have a set of figures which seem to us valid. Our fundamental determinations are taken with the subject reclining with the forearm at sternal level. The plethysmograph is not very long, about 150 cm, it has a thin rubber sleeve and the brass outside - I'll omit our trials with leaks! At the ends of the plethysmograph are rather loose rubber cuffs which hold it on, the upper one anchored by surgeon's plaster to the arm. Around these rubber cuffs, to prevent bulging of the inside bag are narrow inflatable bags, boun[d] on by ordinary bandages. We were much troubled in our earlier types of plethysmographs by vasomotor changes. These we hope we eliminate, following an idea of Dr. Landis', by taking the volume of the arm segment with the blood squeezed out of the vessels. The program is this. After the apparatus is in place and preliminary performances have properly arranged the water in the rubber bag so there are no bubbles and so the bag will come back neatly to a constant size afer pressure is put on it, we try to determine the arm volume at rest, by a series of three determinations which must check within 0.5cc. A high pressure is thrown on the upper arm to stop the entrance of blood, about 230 mm Hg, a pressure of 55 cm H2O is put into the narrow cuffs at the ends of the plethysmograph to prevent bulging and the same pressure on the water inside it, and hence on the arm underneath. The arm promptly shrinks as the easily moved blood is driven from this segment to the part of the arm between plethysmograph and high pressure bag. This amount is measrued by a levelling burette, always kept at the level of the plethysmograph. The flow gradually stops and in about five minutes we come to an approximate end-point, arbitrarily chosen as the time when only 0.2cc moves in two successive 30 sec. If the determination is continued longer the very slow change continues at this rate, approximately for at least five minutes more - we have not gone farther. After the pressures are removed and the resultant hyperemia is over, we can repeat the test and get the same end-point. This we think of as the volume with collapsed vessels.
Then we put on the upper arm any pressure we choose, from 15cm H2O to 50, for a period of not less than 15 minutes, often 30 minutes. At the end of that time the arm volume is measured as before, and we find it increases and the pressure used increases. See the little chart for the slope of the line. Our earlier methods gave the same results by an air determination which did not rule out the vasomotor changes, but yet which was evidently getting the same thing, approximately. Filtration seems to begin - if we really are measuring this as we hope, not lower than 15 cm, I think, and not much above 20 cm. We measure the volume of the arm segment used and calculate in terms of cc per minute per hundred cc of tissue.
To see if hydrostatic pressure and colloid osmotic pressure are both involved we have repeated the experiments standing, preferably on the same day as the reclining test. These things are not brief, and the standing is very long. We had one man faint dead on us, one girl get too dizzy to be any use. Dr. Landis has been the best, and I can make it by a little gentle systematic movement of feet and legs, though I have been dizzy somewhat. But we have a reasonable set of determinations, all the same in their result. I've put in the figures for four of them. The filtration is much less in standing - and the colloid osmotic pressure is distinctly higher. We lost some sets of Colloid osmotic pressures because we did not find out that the membrane used in the osmometers did not tolerate oxalate in the slightest excess - that had been used here before. now we use nothing - just centrifuge the blood longer after it has clotted. Many of the earlier figures are probably all right - but I do not like to use them.
We are now working with the disappearance of this liquid which has made the arm bigger. We seem to find that if only a little is put out into the arm it can be kept there by a lower pressure, say even 15 cm H2O, than if there is much. Putting on 30 cm so far has always meant the increase of the volume, but results vary with 20, and according to the amount of liquid previously put out into the arm. We are in the middle of this series now. So far we have not been able to see whether it is probably being put out as lymph - this is one reason why we are so interested in what you are doing - or whether part of it may be reabsorbed into the blood capillaries. And the end of the year is near!
I have also been starting to workwith [sic] venous pressures - we like the method worked out this year very much, a celluloid capsule stuck on by collodion, with pressure from wither a water or a mercury manometer according to what is manted. [sic] I have been trying to find out whether as time passes there is any progressive change in the pressure in the foot veins comparable to the pulse-arterial pressure changes in standing. It is so awfully easy to change that venous pressure by slight movements - and there are other trils [sic] - but yet I think there may be something to get - and that there may be differences between individuals. I have yearned for the tilting table! It may be best to leave this for South Hadley where there are so many girls and the tilting table. Or there may be a preliminary series here.
Professor Krogh and his wife and the two little girls were down at the Canary Islands and stopping off here and there for about two months. We missed them a lot, but we had plenty to do. Dr. Rehberg had a bad case of flu and there are kidney complications which are keeping him in the hospital for at least several weeks more. They do not seem to find a satisfactory cause for the symptoms. He is in Dr. Faber's care, and everything seems to be done to find out - and meantime it is very tedious for him and hard for Mrs. Rehberg. Professor Krogh expected to have this half year free from lectures, but he is taking over the work Dr. Rehberg was to have.
There was a nice Norwegian surgeon here for a while - another comes anon. Next year there is to be a German and somebody from [...] And of course several Danes, mostly young doctors, though one is a very brilliant young man who is making tests on Aviators under low oxygen, carrying them clear down to the point of collapse and testing them psychologically for accuracy of judgment at the end. That work has just begun. The respirator is also being operated - varied somewhat from your model - as you probably know. It looks like a white locomotive with a smoke-tack, running on rubber tired wheels. They tried it for an emergency case, suicide, I think, but it was too late. There was a gathering of the proper authorities from the hospitals and rescue service one day just before the Professor left for the Canaries, quite interesting.
Altogether the year has been an interesting one. I've seen a lot of Denmark and Danish manners and customs, especially dinners! The weather in March has been grand - many sunny days after a decent fall of snow, with everybody wild for two Sundays out in the Dyrehavn, I never saw such a mob out for Ski-ing, coasting, and such. Special trains every few minutes. Perhaps you had such a season when you were here. Now it feels like spring and the birds have begun to come and the early spring bulbs to blossom. Also there is a fine crop of spring poetry in the papers - it must be here.
I wrote a note to Mrs. Drinker more than a week ago but have not sent it because this was to be sent too. I'm sorry my typewriter ribbon is so far gone. Probably I can buy one at any corner stationery, but I have had an idea of hunting up Remington for it.
And I hope the monograph on the lymphatic circulation will be out soon - I need it!
Sincerely yours,
[Unsigned, but written by Abby H. Turner]