Thank-you all for your kind letters and concern. Myst is staying at the vets for now, making sure he eats, has no more constipation and gets shots for antibiotics instead of pills so his digestion is not as affected. He looks forward to coming home. (Terry says visiting is difficult because Myst wants to go home with her, but it is good for Myst to stay there.) He was a little dehydrated too. He is eating now, not as much as we'd like, but then he is a small sickly cat. Shaded Silver Persians are wonderful cats with the best of personalities. Purebred cats are great though breeders need to be even more careful to avoid too closely bred cats with this rarer group of them.
On the other hand, we Himalayans are a hardy group and Dandelion, a mixture of many cats, is probably outliving us all. He is 18 and going strong!