72 THE BODY AT WORK 



the same method if their data allowed of its application. The 

 peculiarity of the data with which Science deals is that they 

 can be brought to a test of which the data of historical, or 

 political, or economic theory are not susceptible. They can be 

 confronted with control experiments. The control experiment 

 is the alphabet and the syntax of the scientific method. No 

 hypothesis is admissible into the pyramid of theory until it has 

 passed this test. A natural phenomenon is observed. Every 

 measurement which is applicable is taken and recorded time, 

 weight, temperature, colour. Scientific observation implies 

 the tabulation of all particulars which are capable of statistical 

 expression. Reflecting upon the relation of the phenomenon to 

 other phenomena of a like nature, the philosopher it is the 

 philosophy of physiologists which interests us formulates an 

 hypothesis as to its cause. At this point the real difficulty of 

 applying the scientific method begins. It is easy to formulate 

 hypotheses. It is very difficult to devise control experiments. 

 An experiment must be arranged which will provide that, 

 while all other conditions in which the phenomenon has been 

 observed to occur are reproduced, the condition which was ex 

 hypothesi its cause shall be omitted. This digression into the 

 philosophy of science may seem to be somewhat remote from 

 our line of march, but it may perhaps hasten our progress in 

 the comprehension of the story of physiology. There is no 

 other science in which the control experiment plays an equally 

 important part. Unless this is realized, the whole trend of 

 experimental work will be misunderstood. Scudamore ex- 

 plained coagulation as due to contact with air. Based on the 

 observations we have cited, no hypothesis could have seemed 

 more reasonable. With a view to checking this hypothesis, 

 blood was received into a tube of mercury. It coagulated in 

 the Torricellian vacuum. Scudamore's hypothesis, like many 

 earlier and later, when confronted with a control experiment, 

 was turned away, ashamed. 



Clotting is a property of plasma. Red corpuscles play no 

 part in the process. Coagulation does not occur in a living 

 healthy vessel. It occurs when the vessel, and especially when 

 its inner coat, is injured. It is hastened by contact with 

 wounded tissues, especially with wounded skin. Contact with 

 a foreign body also starts coagulation. If a silk thread is 



