MICROSCOPIC DRAWING AND ENGRAVING. 



constitution. 87. Magnified view of a dro]>of milk. 88. The butter 

 globules. 89. Their number variable. 90. Analysis of the milk of 

 different animals. 91. Richness of woman's milk. 92. Analogy of 

 milk to blood. 93. Importance of the quality of milk. 94. Its 

 richness ascertained. 95. Quevenne's hydrometer applied to milk. 

 96. Its fallacy. 97. Donne's lactoscope. 98. Objections to it 

 answered. 99. Frauds practised by milk vendors. 100. Fore-milk 

 and after-milk. 101. Self-engraved photographic pictures. 



64. DR. BONONIO, having directed his researches to the itch 

 insect, found that it was very nimble in its motions, covered with 

 short hairs, and furnished with a formidable head, from which a 

 pair of strong mandibles projected. 



At the extremities of its four pairs of legs, there are feet of 

 remarkable form, each of which is provided with a sucker, by 

 means of which he inferred that it sucks or draws its way under 

 the skin, having first excavated a space for itself with its man- 

 dibles. The insects form their nests there, deposit their eggs, and 

 multiply rapidly. 



65. More recently, Dr. Bourguignon has studied the habits of 

 this insect by means of a microscope specially adapted to the 

 purpose, and has confirmed the discoveries of Bononio. He found 

 that the insect fastens itself in the furrows of the skin by means 

 of the suckers of its feet, aided by small bristles, being likewise 

 covered with similar bristles in various parts of its body, by which 

 it fixes itself more firmly, while it works its way with its man- 

 dibles ; it is not furnished with eyes, but in a moment of danger 

 it quickly draws in its head and feet, this motion and that of its 

 gait resembling those of a tortoise. It usually lays sixteen eggs, 

 which it deposits, ranged in pairs, in the furrows under the 

 skin, where they are hatched in about ten days.* 



66. The insect which produces or accompanies the mange in 

 horses, and which is called the acarm-exulcerans, is represented 

 in fig. 37, p. 49, magnified in its linear dimensions one hundred 

 and fifty times. 



67. This animalcule is larger and more easily obtained than 

 the former ; it is found under the whitish scales which are de- 

 tached from the skin of the horse, and if several individuals be 

 taken, they will be found to be in different states of development, 

 having four pair of legs when full grown ; the two foremost pairs 

 are terminated in a strong and sharp claw, and their general form 

 is like that of the legs of a fiea, consisting of five joints or 

 segments. 



The head consists of nothing but a mouth, in which the organs 

 of mastication are seen, consisting of a pair of very fine and sharp 



* Bourguignon, quoted by " Hogg '' on the Microscope, p. 318. 

 98 



