360 



BIOLOGICAL EFFECTS OF RADIATION 



gives the values of the term k in the unimolecular reaction isotherm 



k = -log — — 

 t a — X 



after different exposures, and might be interpreted as showing that the 

 fundamental reaction proceeds at a rate proportional to the concentration 

 of a single disappearing molecular species. Other possible interpretations 

 are not excluded. 



Lundberg obtained better agreement in single experiments than did 

 Brooks. This was perhaps due to his irradiation of undiluted serum 

 (hog), since he found dilution prior to irradiation to conduce to irregu- 



100 



90 



80 



70 



"c 60 



^ 40 



4) 



50 



20 



10 











10 



50 



60 



70 



20 30 40 



Time in Hours 

 Fig. 2. — Alexin titer as affected by X-rays. Ordinates: alexin titers; abscissas: time. 



(After Chambers and Russ, 34.) 



larities of titer and reaction rate. The reason for this is not obvious. 

 Both authors agree in finding photoinactivation to be fundamentally 

 a photochemical destruction of some one substance, or possibly a group 

 of very similar substances with the same photosensitive atomic groupings. 



As already mentioned, Chambers and Russ (34) found during inactiva- 

 tion of alexin by a-rays an initial lag in the process (Fig. 2). Similar 

 curves were found by Brooks for individual sera; in fact, in one case a 

 large transitory increase of alexin titer was observed during the first 

 3 to 4 min. Chambers and Russ apparently did only one experiment, and 

 their observation may well be atypical like similar observations by Brooks. 

 On the other hand, their method of titration obviously permits errors 

 of at least 10 per cent and possibly more in individual determinations of 

 alexin titer, and errors of this magnitude might account for the whole 

 deviation of their time curve from its expected exponential form. Diffu- 

 sion must also be taken into account in their experiments, since all the 

 radiation was absorbed in a small part of an unstirred sample. 



However this may be, it is well to bear in mind the possibility sug- 

 gested by them, and independently given in more detail by Brooks (29), 



