THE RADIOACTIVITY OF POTASSIUM FROM HUMAN SOURCES.

A comparison of the radioactivity of potassium from human and commercial sources indicates that the radioactive isotope K(40) is probably 1 or 2 per cent less abundant in human potassium.

ON THE RELATION OF DIRECT CURRENTS TO CONDENSER DISCHARGES AS STIMULI.

Data on the electrical stimulation of sciatic-gastrocnemius preparations of the frog by both direct currents and condenser discharges at the same time are discussed in relation to the validity of the differential equation See PDF for Equation where p is the local excitatory process, V the stimulating current or voltage, and K and k are constants. It is concluded that the constant k is the same whether it is derived from the data of the one stimulus or the other when the same fibres are being stimulated.

CONDUCTION IN NERVE FIBRES.

Data by E. A. Blair and Erlanger on the voltage-capacity curves and the nerve impulse velocities of each of several fibres in the same nerve trunk are related to Rashevsky's equation for the velocity of transmission in nerve.

THE DIFFUSION OF CARBON DIOXIDE IN TISSUES.

1. Two methods are given for measuring the rate of diffusion of CO(2) in tissue membranes. Methods are also given for the determination of tissue thickness and the absorption coefficient for CO(2) in tissues.

THE POTASSIUM EQUILIBRIUM IN MUSCLE.

1. Analyses were made of the K and HCO(3) content, the irritability, and weight change of isolated frog sartorius muscles after immersion for 5 hours in Ringer's solutions modified as to pH and potassium content. 2.

ROENTGEN RAY INTOXICATION : IV. INTESTINAL LESIONS AND ACUTE INTOXICATION PRODUCED BY RADIATION IN A VARIETY OF ANIMALS.

These experiments show that the common laboratory animals are about equally sensitive to the x-ray given over the abdomen. The clinical reaction following a M.L.

ROENTGEN RAY INTOXICATION : III. THE PATH OF A BEAM OF HARD RAYS IN THE LIVING ORGANISM.

X-rays which injure intestinal epithelium (and presumably other body or tumor cells) travel in straight lines from the target through the living tissues, forming a cone or beam of rays as controlled by impervious screens. It is probable that secondary radiation is formed, especially deep in the body tissues, but such radiation does no injury to intestinal epithelium outside of the cone or path of radiation. Lesions in the stomach and intestine may be confidently predicted from a knowledge of the size and form of the cone or beam of x-rays given over the abdomen.

ROENTGEN RAY INTOXICATION : II. THE CUMULATIVE EFFECT OR SUMMATION OF X-RAY EXPOSURES GIVEN AT VARYING INTERVALS.

A single large dose of x-rays over the abdomen will cause a definite injury of the mucosa of the small intestine and the severity of the clinical intoxication seems to parallel this recognizable epithelial injury. This clinical intoxication lasts 4 to 6 days if the x-ray dose is sublethal. Subsequent doses of radiation given within this period of clinical intoxication give recognizable evidence of summation or a cumulative effect.

ROENTGEN RAY INTOXICATION : I. BACTERIAL INVASION OF THE BLOOD STREAM AS INFLUENCED BY X-RAY DESTRUCTION OF THE MUCOSAL EPITHELIUM OF THE SMALL INTESTINE.

The x-ray has a specific effect upon the epithelium lining the crypts and covering the villi of the small intestine. A suitable dose of x-ray will destroy this epithelium in large measure, leaving empty crypts and naked villi exposed to swarms of bacteria in the intestine. Subsequently one does not observe an overwhelming invasion of the tissues, lymph, and blood by intestinal bacteria.