GKAPIIIC KEPHESENTATION OF EXPERIMENTS. 



289 



Experiment II, Noxemher 9, 18 — . 



Old rabbit. Weight, 1764 grainmcs. Jugular vein exposed. 

 Animal not narcotised. Cannula in the left carotid. Animal 

 otherwise uninjured. 



Gra-pliic Method of Representing Experiments. — In looking 

 over a column of figures such as tlie tables we have now 

 obtained, it is by no means easy to see at once what it really 

 indicates ; and it is still more difficult when we have to com- 

 pare several tables together. For this reason it is of great 

 advantage to convert the tables into curves, from which the 

 result of any experiment can be learned at a glance, and the 

 points of resemblance, or difference in the results of a whole 

 series compared with the greatest ease. 



To obtain these graphic curves, we reverse the process by 

 which we formed our tables. We first take a piece of paper 

 ruled in squares, and on it we draw a horizontal line or abscissa, 

 and then a perpendicular to one or both ends, and number the 

 spaces along both tlie abscissa and tlie perpendicular or ordinate. 

 Those along the abscissa represent periods of time to which we 

 may assign any value which is convenient, seconds, minutes, 

 hours, or multiples of these. The numbers along the ordinate 

 may represent blood-pressure, pulse-rate, number of respirations^ 

 or degrees of temperature ; and we may describe curves repre- 

 senting all of these on the same paper, distinguishing them from 



