PREFACE 



This manual is prepared as a laboratory text for students pri- 

 marily interested in dairy cattle breeding. A good training is 

 desirable in the elements of biology including courses in pure gen- 

 etics, cytology, and the mathematics of statistics before commencing 

 this work in the agricultural college. Desirable students need not 

 be excluded from the course, however, if they lack courses in these 

 subjects. It will simply mean that such students will have to do 

 outside reading in such texts as T. H. Morgan, 1919, Physical 

 Basis of Heredity, Lippincott Company, Philadelphia; T. H. Morgan, 

 A. H. Sturtevant, H. J. Muller, and C. A. Bridges, 1915, The 

 Mechanism of Mendelian Heredity, Henry Holt and Company, 

 New York; Babcock and Clauson, 1918, Genetics in Relation to 

 Agriculture, McGraw-Hill Book Company, New York; G. Udny 

 Yule, 1919, fifth edition, An Introduction to the Theory of Statistics, 

 Lippincott Company, Philadelphia. 



The basis for the lecture course to accompany the laboratory 

 course is found in the text, Milk Secretion, 1924 (Williams and Wil- 

 kins Company, Baltimore). The citations to reading in this text are 

 indicated by the abbreviations M . S. The citations to other sources 

 are indicated by rather complete references. No effort is made to 

 give references to general genetic or physiological literature as it is 

 believed that these courses are better given in the pure science sec- 

 tions of the University than in the Agricultural College proper. 



It is fairly obvious in a course of this kind, necessarily limited for 

 time, that the work had better be confined in general to one breed 

 of dairy cattle. This breed may be changed from year to year 

 indicating to the student that the results for, the different breeds 

 correspond quite closely in the principles involved. By following 

 through this outline with dairy cattle the student will obtain an 

 excellent foundation on which to study similar problems in other 

 types of livestock, horses, sheep, swine, etc. A rather complete 

 list of papers relating to cattle breeding is found in the bibliography. 



