10 



The crystals will be of the same form and size as those 

 made from mammalian blood. Teichmann's crystals can 

 be obtained from blood stains no matter how old, hence their 

 presence is often of value in medico-legal cas"es. Remem- 

 ber that the fact that Teichmann's crystals can be obtained 

 from a stain only shows the presence of blood and nothing 

 more ; they can be obtained from the haemoglobin of any 

 red blood cell. 



(d) Detection of Red Blood Cells in a Dry Clot 



of Mammalian Blood. 



Take a small portion of a dry clot, place it. on a slide, and 

 cover it with several drops of a 33% solution of potassium hydrate. 

 After the clot has become somewhat softened, break it up into as 

 small pieces as possible with your teasing needles, and cover with 

 a cover glass. Set it aside for 5 to 10 iniuutes, then gently tap the 

 cover glass with a teasing needle. 



Examine to see whether any of the corpuscles are free; 

 if so, determine their shape and size; if not set aside 

 awhile and try again. 



(e) Detection of Red Blood Corpuscles in a Dry 



Clot of Pigeon's Blood. 



Prepare as (d) of this lesson. 



Search for the oval red blood cells; you may be able 

 to make out a nucleus in them. 



