334 The Ultra-Violet Absorption Spectra of Blood Sera. 



most strongly modified, but the whole band may be greatly reduced, with its 

 head thrown towards the extreme ultra-violet. 



Tuberculosis has been the subject of inquiry in 27 cases ; 10 of them 

 exhibit a band of slightly increased extinction in section /3 between wave- 

 lengths 3200 and 3500. Another ten show a tendency to some ill-defined 

 absorption in the same regions, or an increase in the step-like prominence 

 at the foot of section 7. The remaining seven were all " mild " cases, and 

 caused no special absorption. However, some others similarly described were 

 not distinguishable from those marked " severe." 



In four cases of anaemia the serum presented no abnormality. Miscel- 

 laneous cases of rheumatism, rheumatoid arthritis, cirrhosis of the liver, etc., 

 have afforded irregularities in the curve, but confirmation is needed to 

 establish their significance. 



Review. 



So few natural substances of unknown constitution appear to have 

 been submitted to direct examination by ultra-violet absorption spectro- 

 graphy, that the success attending the present investigation of serum is the 

 more gratifying. 



Practically all the properties of the absorption curve of normal serum have 

 proved to be constant and characteristic, while there is enough variation in 

 minutiae to stimulate a closer investigation, with a view to ascertaining the 

 range and causes of the variations, and the much greater, though still 

 small, changes associated with certain pathological conditions make the 

 inquiry all the more urgent and interesting. The method lends itself to 

 the purposes of clinical practice, for so small a quantity as four or five drops 

 of blood collected* in a capillary tube suffice for a complete examination in 

 the ordinary way. Again, no preparation whatever of the specimen is 

 necessary except to separate the serum in the containing tube by means of 

 the centrifuge, and then to transfer it to the observation cell. 



It is improbable that any important improvement will be made in the 

 qualitative properties of the absorption curve as described above. The 

 extinction coefficients are, however, only approximately quantitative. The 

 greatest hindrance to reaching the final goal has been the lack of a 

 sufficiently perfect spectrophotometer. It is worthy of emphasis that the 

 work described has been done on the two most modern and most accurate 

 instruments available, which have proved adequate for most academic 

 requirements. But the exacting demands of the serum work reveal the 

 necessity for one still finer. The author has designed a new photometer, 

 which is now under construction, and will, it is hoped, supply the need. 



