GESTATION. ' 119 



the bicoxo-femoral 7t'o inches. Another Cow was i2>^ hands high, 

 the width of croup iSy^ inches ; the weight of the foetus was about 

 seventy-three pounds, the sterno-dorsal diameter 103^ inches, the bi- 

 scapulo-humeral 6 inches, and the bicoxo-femoral 8Vo inches. With a 

 Cow \2Y^ hands high, and croup 18 inches in width, which had experi- 

 enced a protracted accouchment in consequence of the size of the calf, 

 and which had aborted the previous year, the weight of the foetus was 

 sixty-six pounds, the sterno-dorsal diameter 15 inches, the biscapulo- 

 humeral 7^ inches, and the bicoxo-femoral 8^^ inches. 



CHAPTER V 

 Gestation. 



Gestation, or pregna?icy, comprises the period during which the female 

 animal carries its young while this is undergoing development. Its con- 

 sideration is of much moment, and we will, with regard to it, study it in 

 this chapter from a normal physiological point of view : noticing the 

 anatomical and functional alterations attending.it, the mode of recogniz- 

 ing it, its duration in various species of animals, and the exceptional 

 departures from the usual law, with respect to the number of young pro- 

 duced. 



SECTION I. MODIFICATIONS IN THE UTERUS DURING PREGNANCY. 



With the development of the foetus, the uterus undergoes important 

 anatomical and physiological modifications, while the system of the 

 mother also participates more or less generally in the phenomena which 

 mark the period of gestation. The modifications and phenomena are 

 worthy of attentive notice, not only from the importance they hold with 

 regard to the reproduction of animals, but also from the practical issues 

 involved in the study. 



The anatomical changes in the uterus are those relating to its volume, 

 structure, form, situatmi, and direction. 



Volume. 



W^th regard to volume^ we have seen that during and after copulation 

 the uterus is congested, and that, when conception has taken place, the 

 thin pulpy secretion corresponding to the decidua of the human female 

 covers its' internal surface. The vessels, distended with blood, gradually 

 enlarge to a great size : from the smallest to the largest forming most 

 intricate and beautiful plexuses on and in the texture of the organ. The 

 coats of the arteries are thickened to compensate for their distention, 

 and the additional labor they have to perform ; wdiile the veins are still 

 more enlarged in calibre. The lymphatics are likewise augmented in 

 number and dimensions ; and the nerves, which were comparatively 

 small in the unimpregnated state, enlarge and anastomose so freely as to 

 compose a network similar to that of the vessels — the increase taking 

 place in the nerve termina, not in the nerve substance. 



