Heat coagulation of serum in cancer; a method applicable to very small quantities of serum.

The method recently described by Huggins, Miller, and Jensen (1049) for measuring defects in the coagulation mechanism of the sera of cancer patients cannot be applied without modification to the sera of small experimental animals because the quantity of serum required is too large. By substi tuting a measurement of the opacity of the heated serum for a measurement of its coagulability (or inhibition of coagulation by iodoacetate), values which are well correlated with the iodoacetate in dex of Huggins, Miller, and Jensen can be ob tained; these opacity measurements require a very small amount of serum, and are as applicable to the sera of small animals as to that of man. Method.—0.05 ml. of serum is added to 0.75 ml. of a NaCl-buffer (four parts of 2.2 per cent NaCI plus one part of a mixture of M/15 NaH2CO3 and M/15 Na2HCO3) at pH 7.O. The mixture, contained in a small test tube, is placed in a boiling water bath for 30 minutes and is then allowed to cool. The extinction coefficient E of the opaque contents of the tube is found with a microphotometer which has a chamber 1 cm. in depth and has a capacity of about 0.5 ml.; this microphotorneter can be constructed by using a microscope tilted horizon tally and fitted with a Lange thermopile in place of the eyepiece, together with a potentiometer circuit for measuring the thermopile current. The cham ber is fixed on the stage of the microscope in the line of the light path, and the light source is a lamp with a (530 m/i filter. The microphotometer is cali brated by inserting neutral filters with known ex tinction coefficients in the path of the light, the thermopile current corresponding to each filter be ing measured; this provides a graph from which potentiometer readings can be translated into ex tinction coefficients of the opaque diluted serum in the chamber. The total proteins in the serum are found by a gradient tube density method (2), which requires only a small drop of serum. The extinction coeffi cient is then divided by the total protein to give the opacity (as a value of E) per gram of protein,