184 IOWA ACADEMY OF SCIENCE Vol XXIX, 1922 
17 except it was stretched with a ten gram weight for ten min- 
utes' before being stimulated. 
Figures 19, 20 and 21. These are series treated the same as 18 
except that the ten gram weight stretched the muscles for twenty 
minutes, one hour and fifteen minutes, and three hours, respec- 
tively. When compared with the corresponding sodium chloride 
series, 14, 15 and 16, they show the inhibiting effects of potassium 
chloride on the contraction of the tissues*. 
Figures 22 and 23. The former is a record of an unstretched 
muscle in normal potassium chloride while the latter is comparable 
with it. The only difference is*that in 23 a twenty gram weight 
was applied for ten minutes. Figures 23 and 18 are also simi- 
lar, the only difference being that the former was stretched with 
twice the amount of weight as the latter. The greater sensitiza- 
tion is much more apparent where the stretch was greater. 
Figures 24, 25 and 26. These series are comparable to 19, 20 
and 21, respectively, differing only in being stretched with twice 
the amount of weight, The onset of fatigue is sooner and its 
progressive effects are more pronounced where the greater weight 
is used. 
Figure 27. In this series normal calcium chloride was used 
and the series is comparable to 12, 17 and 22. The initial con- 
traction is much greater, showing that the process of sensitiza- 
tion has taken place more quickly. 
Figures 28, 29, 30 and 31. This series is similar to 27 and 
comparable with series 13, 14, 15 and 16, respectively, and also 
with 18, 19, 20 and 21, respectively. The only difference in the 
treatment is in the kind of solution in which the tissues were 
immersed. 
BIBLIOGRAPHY 
1. Buddington, R. A., ’02, Am. Jour. Phys., Vol. VII, page 155. 
2. Eddy & Downs, *21, Am. Jour. Phys., Vol. LVI, page 182. 
3. Harrison, B. M., and Baldwin, F. M., Proceedings of the Iowa 
Arademy of Science, Vol. 28. 
4. Harrison, B. M., ’23, Science Jan. 19, page 87. 
Department oe Zoology and Entomology, 
Iowa State College. 
