Erytlirocytes have long been used for permeability studies but in spite of their colivenience, considerable care must be exercised in interpreting observations because of the sensitivity of these cells to environmental changes. In most of his writings, ,Jacobs has emphasized this point. During the past few years the author lias been interested in tryitig to find a method for detcimiriirig changes in the permeability to norielectrolytes of erytlirocytes which have beeti subjectcd to 1-ather niarlied eiivironniental changes, witliout too much danger of misiiiterprctation resulting from other alterations in tlic cells. Sirice liernolysis times may be influenced hy a variety of factors (see, f o r example, Jacobs arid Parpart, '31), ii more wnsitive apparatus was constructed (Hunter, '49a) in ortlrr to use 1-atc.s of swelling as a measure of pernieability.
Hut it was soon found (Hunter, '49b) that this technique was riot too satisfactory, since slight liernolysis occurs under a variety of circumstances which makes it difficult to interpret tlie results obtained.
This nork \ \ a s supportcrl in part h y grants from tlic 1)jvkion of Grants and Rescnrcli, IT. S. Public Health Serlice arid tlir Faculty Rescnrcli F u n d , The T n iversity of Ok1:ihom:i.
The ex1ieIinieiit;il n o 1 k WIS pcrfoi med in tlie Depirtiiient of Zoological Srirnccs, Tlrcl ITnivei sity of Okl:ilioma, Norman, Okln.