vi PREFACE 



which a knowledge of mammalian embryology is the objective, 

 ordinarily pass from the study of three or four day chicks to 

 work on mammalian embryos. 



While the text has been kept brief, illustrations have been 

 freely used in the belief that they convey ideas more readily 

 and more accurately than can be done in writing. Direct 

 labeling has been used in the figures to facilitate reference to 

 them. Most of the drawings were made directly from prepara- 

 tions in the laboratory of Histology and Embryology of Western 

 Reserve University School of Medicine. However, figures from 

 other authors, particularly Lillie and Duval, have been used 

 extensively for comparisons and for schemes of presentation. 

 Several figures have been reproduced directly or with only 

 slight modifications. These are designated in the figure 

 legends. 



I wish to acknowledge the assistance I received in the prepa- 

 ration of material by Mrs. Mary V. Bayes, and in the drawing 

 of the figures by Mrs. Bayes and Dr. Louis J. Karnosh. I am 

 also indebted to my father, Prof. Wm. Patten of Dartmouth 

 College for criticism of the figures, and to Dr. F. C. Waite of the 

 School of Medicine, Western Reserve University for his helpful 

 interest and cooperation in all phases of the preparation of the 

 book and especially for his reading of the manuscript. 



BRADLEY M. PATTEN. 

 Western Reserve University, 

 School of Medicine. 

 Cleveland, Ohio. 



