Angular 2: How to access an HTTP response body?

Both Request and Response extend Body.
To get the contents, use the text() method.

this.http.request('http://thecatapi.com/api/images/get?format=html&results_per_page=10')
    .subscribe(response => console.log(response.text()))

That API was deprecated in Angular 5. The new HttpResponse<T> class instead has a .body() method. With a {responseType: 'text'} that should return a String.