CONTENTS, 



Department Bulletin No. 51. — A Bacteriological and Chemical Study of 



Commercial Eggs in the Producing Districts op the Central West. Page. 



Introduction 1 



Freeh eggs 3 



Chemical composition 5 



"Market fresh " eggs 6 



Relation between bacterial multiplication and chemical changes 7 



Examination of eggs opened aseptically in the laboratory 9 



Stale eggs 9 



Eggs having settled yolks 12 



Eggs changed by incubation 13 



Eggs having dirty shells 17 



Eggs having cracked shells ,^ 22 



Eggs having the yolk seeping into the white 27 



White rots 29 



Eggs having yolk adherent to shell (spot rots) 30 



Moldy eggs 33 



Black rots 38 



Composite samples of eggs opened commercially in the packing house 39 



July and August firsts 40 



Seconds 41 



Eggs having dirty shells 43 



Eggs having cracked shells 44 



Eggs having the yolk partially mixed with the white 47 



Bloody whites 49 



Eggs with blood rings 49 



Eggs with turbidity in thick white 51 



Eggs having white partially coagulated by heat 52 



Eggs having entire white turbid 52 



White or Light rots 53 



Eggs having the yolk adherent to the shell 54 



Black rots 56 



Deteriorated eggs not distinguishable by candling 56 



Summary 65 



Bacteriological results of individual eggs opened aseptically in the 



laboratory 65 



Bacteriological and chemical results of composite samples of eggs opened 



commercially in the packing house 68 



A comparison of bacterial contents of individual eggs opened asep- 

 tically with those of eggs opened commercially 73 



Technique for the bacteriological examination of eggs 74 



Methods used for obtaining samples of individual eggs opened asep- 

 tically in the laboratory 74 



Preparation of composite samples of eggs opened commercially in the 



packing house 74 



Culture media used 76 



Analytical methods used in the ' ' egg investigation " during the summer 



of 1912, at Omaha, Nebr . . 76 



in 



79688—15 



