THE SCOPE OF ZOOLOGY 



were thousands of children in each group ; and, since they were taken at 

 random, there was no reason to believe that there would be any over-all 

 difference in the chance of exposure, nor of the initial susceptibility to 

 the disease of the two groups. Those who received the inoculation 

 were listed as the experimental group, and those who did not receive it 

 served as the control group. Careful records were kept of the cases of 

 this disease and the severity of these cases among the two groups. 

 Much to the disappointment of all concerned, the doctors found at the 

 end of the summer that there was no significant difference in the num- 

 ber of cases nor the severity of the attacks between the two groups. 

 They were, therefore, forced to conclude that the serum was useless as 

 a preventive of this disease. If this experiment had been made with- 

 out the control group, the physicians would not have been certain that 

 the serum did not have some value and might have gone on using it 

 for years. With this evidence, however, they were motivated to con- 

 tinue research along new lines in their search for a preventive and to 

 cease work with this serum. 



This search proved fruitful, for within a few years another sub- 

 stance was found which gave promise of preventing the disease of polio. 

 Again controlled experiments were arranged — this time during the 

 height of an epidemic in Houston, Texas. Thousands of children were 

 given the newly discovered substance (gamma globulin) which was 

 obtained from the mixed blood plasma of many people. Thousands 

 of others were given injections of plain water with a little salt in it. 

 This second group served as a control. In this case the children who 

 had taken the gamma globulin showed an almost complete absence of 

 the disease for about five weeks, while the number of cases was rather 

 high in the control group. With this information as a guide, additional 

 work was carried out and the gamma globulin indeed did prove to be 

 of value in short-term prevention of polio. At about this time, how- 

 ever, the Salk vaccine for polio was developed which promised a more 

 lasting protection from the disease. Another extensive program of con- 

 trolled experiments was undertaken involving hundreds of thousands 

 of children in all parts of the country. These experiments show us the 

 value and actual necessity of controls in any experimental investiga- 

 tions. 



The Scientific Attitude 



The scientific attitude is one of the most necessary yet hardest to 

 achieve phases of scientific investigation. The scientific attitude in- 

 volves an unbiased evaluation of the facts without influence by per- 



