Transcriber’s Note:
Illustrations have been moved to paragraph breaks near where they are mentioned.
Punctuation has been made consistent.
Variations in spelling and hyphenation were retained as they appear in the original publication, except that obvious typographical errors have been corrected.
Changes have been made as follows:
The notation 1 2 for fractions has been changed to 1/2.
p. [11]: muste la changed to mustela (invest mustela vulgaris)
p. [30]: 5 changed to 6 [(Fig. 6). The]
p. [39]: Fig. 6 referenced here does not exist.